Writing is hard work: when you order through links on my site, I may or may not earn a small commission.

What is the Reef-Safe Ich Treatment for Fish in a Display Tank?

It’s really discouraging to see your aquarium efforts go to waste because of a single parasitic outbreak.

A reef-safe treatment for fish with marine Ich exists but it requires a bit of dedication and a couple of inexpensive gadgets.

In fact, I’ve tried what I’m about to describe on two separate aquarium systems and it worked flawlessly both times.

You’ll be able to save your ill fish without harming your corals and invertebrates or having to set up a new tank.

In this guide, I will teach you how to safely treat the Ich parasite in your display reef tank and show you the science that backs my methods up. But if these methods are so efficient, why aren’t more people talking about them?

What is the reef-safe Ich treatment?

When my aquarium was first faced with the parasitic outbreak I sat down and thought in depth about a solution.

I came to the conclusion that the only approach that stands a chance of working while being safe for my reef tank was an Ich treatment that targets the fish and not the aquarium water.

After doing some research I stumbled upon some very promising information which I then tested and had success with.

Here’s the kind of treatment that will safely work against marine Ich in a reef tank:

There are reef-safe methods such as water oxidation and switching to quality foods that help saltwater fish to build up a natural immunity toward the Ich parasite. If these treatment methods are applied on time and for a continuous period, the fish would be able to successfully overcome the Ich infection on their own.

Note that there’s no known medication that can eradicate marine Ich from reef fish while being harmless to corals and other invertebrates inside a display tank.

Clearly, you will get rid of the entire issue by building up the immune system of your aquarium fish rather than trying to eradicate the parasites from your display tank.

The former requires little work and is easy on the fish whereas the latter is often impractical and stressful for them. Also, if you’re not sure whether it is actually Ich you’re fighting, consulting with a vet might be a smart idea.

Who is this treatment method for?

The usual go-to method of treating saltwater Ich is setting up a hospital aquarium and relocating the ill fish there.

In the meantime, you’ll want to wait for the parasites in the display tank to die out which takes about 2.5 months.

Without a host in the main reef aquarium, Ich will complete its life cycle and be done with.

Nevertheless, capturing 10 or more saltwater fish in a 200-gallon reef tank with custom rock work is nearly impossible at times.

Not to mention the great deal of stress this can cause to a fish that already has its immune system compromised.

You could just helplessly wait for all of your marine fish to perish and then leave the aquarium “fishless” for 76 days, true.

That’s hardly anyone’s desired course of action though.

The treatment I’m about to describe is ideal for people who don’t want to spend hours chasing fish around their reef tank with a questionable success rate.

Another decent argument for going down this road would be that most of us won’t necessarily have the means to set up a separate hospital fish tank and maintain that for the upcoming months.

It requires space, resources, time, and experience.

Before I tell you what worked for me I need to make a few clarifications.

What can you expect during and after the treatment?

My reef tank treatment method will not kill Ich.

The parasite will likely remain in the system, but it will be kept under control.

The method allows for your ill saltwater fish to safely handle the symptoms and build up their immune system enough to fight Ich on their own.

There’s plenty of research showing that fish can build up a natural immunity to marine Ich.

At this point, some aquarists may argue that letting the parasite survive inside the aquarium will be somewhat inhumane.

However, that’s hardly the case as this happens literally all the time in the ocean.

In the wild, saltwater Ich, also known as Cryptocaryon irritans, is constantly present in seawater.

So how do marine fish handle it all the time?

Simple – dilution of the parasitic numbers, which allows the healthy fish to successfully fight it off with the help of a good immune system.

I’m about to tell you how to replicate just that and avoid having to tear down your reef aquarium.

You’ll keep the number of parasites in the aquarium water in check while giving your saltwater fish the upper hand.

My experience has been that this way the fish will live a normal and happy life for years to come.

Ich control works and has been working for many of us with successful reef aquarium systems.

It’s important to remember that the treatment method I’m about to describe is meant to be carried out inside of a display tank that also houses corals and invertebrates.

That’s somewhat of a luxury given how fragile these creatures are.

Nevertheless, this method should be regarded as a last resort, when no other option for treatment seems feasible.

If an opportunity to set up a hospital aquarium opens, you should probably do that.

Treating fish infected with marine Ich in a separate tank gives you a realistic chance to get rid of the parasite once and for all.

If you have the time and resources to do that you can look up “saltwater Ich” in the search bar of this website and give my in-depth article on the subject a good read.

The search bar is located in the upper right corner on desktop devices and at the bottom of the page on mobile ones.

Let’s cut to the chase.

How to treat saltwater Ich inside of a display reef tank?

In this step-by-step guide, I will tell you how I managed to successfully banish Ich from a display aquarium with corals in 2 out of 2 tries.

I first tried this method out of desperation in my own reef tank and the second time was when I was advising my good friend who owns a massive 200-gallon system with plenty of SPS and LPS corals.

Both times I was able to completely stop the ongoing fish mortalities and the outbreaks never returned.

In the following years, we were able to introduce new fish to our reef aquariums without any issues. On rare occasions, a newcomer fish would develop a few white spots, but then the spots would completely disappear and the fish would move on with its life.

With that being said, I can share how I achieved all of this without harming our reef corals, along with my reasoning behind each step.

Follow these exact steps to properly treat marine Ich in a display reef tank:

1. Set up an aquarium Oxydator with a 12% Hydrogen Peroxide solution.

Hydrogen peroxide (H2O2) is a well-known oxidant that kills microorganisms through oxidation.

Oxidation is the release of highly reactive oxygen radicals, which strip electrons from the walls of cells, destroying microorganisms in the process.

After desperately searching for a treatment method that would also be safe for my reef corals I stumbled upon a couple of promising reports.

They would describe successfully managing an Ich outbreak in a display tank with Hydrogen Peroxide.

It’s important to note that none of these people reported a negative effect on their established aquarium biofilters.

Being able to preserve my biofilter was more than welcome and actually in line with what the USGS found from reviewing multiple studies on the subject.

Anyway, I was already aware that Hydrogen Peroxide is safe for corals and other marine invertebrates because people were using it to fight cyanobacteria in their reef aquariums for years.

I then used my research skills and dug down further.

Evidently, there’s a study that describes Hydrogen Peroxide killing marine Ich theronts (free-floating stage of the parasite’s life cycle).

During my research I found another study showing scientific proof of H2O2 eradicating the Amyloodinium parasite, also known as Marine velvet.

Both marine velvet and Ich are external protozoan parasites with very similar life cycles so I decided that it makes sense to give Hydrogen Peroxide a try.

Before I continue I need to make sure you’re familiar with the life cycle of marine Ich:
marine ich life cycle
During an outbreak, the Ich tomonts release infective theronts sporadically.

This means that the release is not coordinated between Tomonts and could happen at irregular intervals.

On the other hand, Hydrogen Peroxide degrades in just a couple of hours in aquarium water, because of the many organics found in a reef aquarium.

I also knew that the tomonts would only hatch between 2 AM and 9 AM.

All of this made me give up my initial intention to dose the Hydrogen Peroxide manually.

I could only do so a limited amount of times and each dose would last 1 to 3 hours in the water.

I needed a device of some sort that would allow me to continuously supply the chemical in the reef aquarium.

This way the oxidation process would kill the Theronts whenever they are released from the Tomont cysts.

After some more research, I came across what’s known as an Oxydator.

An oxydator is exactly that – a device that would slowly release Oxygen molecules and Hydrogen peroxide in the aquarium over time.

On top of being perfect for my situation the device itself was very inexpensive, and, evidently, works without the need for electricity or batteries.

I quickly found the most reliable brand based on what people were saying online and ordered.

I went with this Oxydator both times I tried this treatment method.

Oxydators are not easily found in the US but Amazon usually has a steady supply.

Mind that, for this to work properly, you need to get one that’s suitable for your total volume of aquarium water.

We ordered the two A versions for my friend’s 200-gallon reef tank, as each A is rated for up to 105 gallons of water.

For my 100-gallon aquarium, I ordered a single Oxydator A.

If the larger version is out of stock you can just order 2 smaller ones to make up for the total volume of released Hydrogen Peroxide, as we did.

Anyway, I was already seeing fish showing the telltale signs of, and dying so I wanted to start the treatment immediately.

Until the Oxydator was delivered, I manually dosed 1 ml of 3% Hydrogen peroxide per 5 gallons of total water volume (sump included), 2 times a day.

I took this dosage based on other reports and it seemed well within the safe range for fish and corals.

I dosed that directly in the display tank and none of my aquatic creatures showed signs of additional stress.

I did the same for my friend’s fish tank where one anemone seemed displeased at first but went back to normal in 2 days.

When you manually dose, make sure to turn off the powerheads for about an hour.

I also made sure to dose right after lights out, and one hour before they turn on because light speeds up the degradation of Hydrogen Peroxide.

This way I was efficiently targeting the release of Theronts during the night and the Hydrogen Peroxide stayed as much as possible in the water.

Make sure to only use a food-grade 3% H2O2 solution with no additives.

You can get that at your local pharmacy.

Anyhow, you will likely witness a positive effect almost immediately after dosing.

What I saw in the next couple of days was the trophonts falling off my fish and the gradual decrease of white spot density on their bodies.

The rate at which it was happening was not in line with the ever-multiplying white dots I was observing before the treatment.

The study I linked to above confirms this effect of Hydrogen Peroxide and the scientists did not attribute it to the natural life cycle of C. irritans.

Anyway, when the Oxydators arrived we set them up and used 2 catalysts per device.

Catalysts are small ceramic pieces that come with the Oxydator and control the release of Hydrogen Peroxide into the water.

The more catalysts you use, the faster the release of Oxygen and Peroxide.

Since with the Oxydators we have more control over the released amount, we both used a 12% Hydrogen Peroxide solution during the treatment.

No corals or fish were harmed or showed any negative reaction to that.

Food-grade solutions with no additives of this strength are commercially available.

Something like this combined with an Oxydator can work safely in a reef tank.

Our saltwater fish began to improve even faster and mortalities ceased completely.

Both times I tried this there were fish that I thought would not make it.

Both times these fish improved and returned to normal behavior.

What not many know is that the most common reason for fish deaths during a severe Ich outbreak is suffocation. The parasites clog the fish’s gills and block their oxygen intake.

Hydrogen Peroxide both oxygenates the water enough for fish to breathe and forces the trophonts to leave their host.

This alone is enough for a fish to get back on track and strengthen its immune system against further infestations.

An additional benefit my friend and I witnessed with the introduction of Hydrogen Peroxide to our reef tanks was the immense improvement of water clarity.

We observed the water becoming crystal clear to the point where our fish looked as if they were floating in the air.

Mind that said water clarity may increase the PAR potential of your aquarium lights because light penetrates clear water easier. Tune them down a bit if you notice symptoms of over-illumination in your corals.

Another bonus of using this reef-safe chemical was the complete disappearance of all cyanobacteria.

It’s worth noting that we were both running refugiums with Chaetomorpha algae, which remained unaffected.

Anyway, I recommend putting the Oxydator directly in the display tank during the outbreak. It will not be the prettiest piece of decor, but you can safely relocate it in the sump after the Ich infestation subsides, in case you don’t like its look.

At this stage, leave it in the display aquarium and refill it when needed (usually in about a week or so).

2. Feed your fish 100% live food with added Omega 3.

By feeding your marine fish only live foods you allow them to strengthen their immune response and fend off the Ich parasite.

My reasoning for trying this was that wild fish live among, not just Ich, but all kinds of pathogens, yet most of the time they’re able to handle them successfully.

Another argument that pushed me to dig deeper into this approach was the fact that I’ve previously seen reef tanks with fish who have survived Ich without being treated with medicine.

This led me to believe that fish could build up a sort of immunity to the parasite.

I found a couple of studies confirming this (I linked to one of those earlier) so I went ahead and kept looking for ways on how to do it.

With having an Oxydator to keep the number of free-floating Ich Theronts in check I only needed a way to help my fish with building up their immune response further.

I had also read enough scientific literature on the subject and already knew that the quality of a fish’s diet is directly linked to its health.

Feeling confident in my knowledge, I decided to stop feeding pellets to my fish entirely and only offer them live, or recently frozen live food.

This way I would replicate the diet of a wild fish, which would introduce beneficial gut bacteria that aquarium fish can’t get from dried, processed pellets.

My reasoning was that I needed to revive the existing gut microbiome of my marine fish by feeding them critters that have their own natural microbiome in them.

I observed behavioral improvement just 2 to 3 days after switching the pellets with the 100% live food regimen.

We repeated the same in my friend’s reef tank.

The fish would stop scratching and would become lively again.

In fact, I ended up maintaining that regimen to this day, and all the fish who went through that outbreak are still alive and healthy.

I only had fish die before starting the combined treatments.

One important thing to remember here is that when your fish are sick with Ich you should feed them at least twice a day.

They need the energy and nutrients in order to fight the parasite off.

I mixed up some garlic with the live food during the outbreak. This way I made sure the ill fish had their share of live food because garlic is a well-known appetite stimulant.

There’s some controversy on garlic and marine fish as some claim that its continuous use damages their liver in the long run.

I could not find any scientific data to support that claim, but, as a precaution, I only use it when needed.

Anyway, you could also add Selcon (see it on Amazon) to the meals, as it is a combination of vitamins, and Omega 3.

Speaking of which, during my research I actually found this study which explains how Omega 3 could actually boost a fish’s immunity and resistance to external parasites.

In fact, the scientists tested their subjects precisely with the saltwater Ich parasite.

This was more than enough proof for me to buy a bottle of generic fish oil with Omega 3 and add some to the live food I was using in my reef tank.

I think the combination of live food and fish oil can, on its own, repel a severe Ich outbreak.

If you’re wondering what Omega 3 source I used, something like this would do.

With time and experience, I came up with a strict rule to only feed my fish food with added Omega 3 in it, because of how beneficial it is to them.

Anyhow, you can use all types of live food for this to work.

Some of the foods my friend and I used were live blackworms, live or frozen Mysis shrimp and, if we could get our hands on it, fresh mussels. White worms are also a good option as they don’t require much care and multiply fairly fast if you’d wish to cultivate them.

In my experience, the best approach here is to order live aquarium food through some of the reputable aquarium vendors online (AquaBid is a good place to start). Most fish stores won’t have enough to supply you with the needed quantities, but you can ask around if you have free time.

Another way to do this is by preparing your own mix of fresh fish food at home:

  1. Find some fresh, whole fish (guts and bones included) and mix it with some shrimp or squid.
  2. If you can buy clams or have a friend who can supply you with worms – throw that in, as well.
  3. Diversify the meal by adding a type of marine algae of your choice.
  4. Add Omega 3 capsules.
  5. Blend the whole thing and don’t forget to include the fish heads and guts.

When wild fish prey they never spit anything out and they are programmed to benefit from all the ingredients of the kill. For this reason, it’s better if you use whole fish in the mix.

Also, don’t forget to add a couple of Omega 3 softgels to the mix before throwing it in the blender.

Anyway, before blending, add water (dechlorinated and purified through Reverse Osmosis and/or Deionization) or your blender will have a hard time.

After that, you can blend the whole thing well, freeze it in a bag and store it in your fridge.

You just cut pieces of the frozen mixture and soak them in aquarium water before feeding.

In any case, something worth mentioning here is to have a good, strong blender in place.

Another thing to consider is the smell of the mixture. You may want to have a separate blender for this, but that’s up to you.

Though it looks unappealing, a good rinse with dish soap will remove the smell from the blender.

How to maintain these results in the long run?

After about 2 weeks of this Ich treatment, your saltwater fish will likely be as healthy as ever.

Your reef tank will also look perfectly clear, because of the oxidation processes inside.

Your corals will remain perfectly safe during the treatment and there will be no losses.

The oxidation processes will also take care of the increased organics in the water that came with the multiple-per-day feeding.

Hydrogen Peroxide will prevent the build-up of ammonia by directly oxidizing a large part of it to nitrate, aiding the biofilter.

So, to keep this beautiful picture going you need to make sure your fish are not stressed.

Here’s how to maintain your reef tank free from Ich outbreaks after the treatment:

  1. Throw in an extra heater. A fluctuating water temperature is one of the most common reasons for stress and a weakened immune system in aquarium fish.

    I really need to emphasize how prevalent and yet overlooked this is.

    What my friend and I did was add an extra aquarium heater or two to our reef tanks. This way we made sure the water temperature remains steady, even during the night, which is when most of the fluctuations happen.

  2. Don’t use a UV sterilizer in conjunction with the Oxydator. If you’re going to use oxidation for Ich control only choose one of these methods and don’t run them simultaneously.

    I won’t get too technical about it, but I did some research and it turns out the combination may prove a little too strong.

    Irradiating Hydrogen Peroxide with strong ultraviolet light causes a reaction known as an Advanced Oxidation Process (AOP). An AOP produces hydroxyl radicals that are multiple times more reactive than any other oxidant that can be used in water.

    I initially thought of combining a UV sterilizer and an Oxydator to combat saltwater Ich, but after greatly improving my knowledge in chemistry I deemed it unsafe.

    I have no idea if the radicals will remain in the tube of the UV sterilizer or simply spread in all of my tank’s water and potentially over-sterilize the water, killing everything in the process.

    Side note: If anyone with a degree in chemistry is reading this, let me know in the comments so I can upgrade this section.

    Anyway, a strong UV sterilizer with a high “dwell time” will also be able to keep the Ich population in check.

    If you want to use that instead of an Oxydator you can click here to visit my guide on choosing the right unit size for your reef tank.

    However, since you want it for pathogen control you should likely get the ones I recommend for tanks that are 50 gallons larger than yours.

    For example, if you want to control Ich in a 75-gallon fish tank, check my UV filter recommendation for 125-gallon tanks or the ones I explicitly mention as being effective against pathogens.

  3. Dilute the Hydrogen Peroxide solution to 6 or 9%. After the outbreak has been handled you do not need to keep the Hydrogen Peroxide solution in the Oxydator at 12% strength.

    Though there would be no problem with that, from my experience a 6 or 9% solution is effective for ongoing maintenance of the reef tank.

    After treating the outbreak, I personally started diluting the 12% Hydrogen Peroxide solution with some RO water to about 9% strength. I have been continuously using that in my reef tank with no ill effect on my fish or corals in the long run.

    You can also relocate the Oxydator to your sump if you don’t like how it sits in the display tank.

  4. Keep feeding live food and Omega 3 to your fish no matter what. Stick with the live food regimen and stay away from pellets as this will keep your saltwater fish in top shape.

    Your fish pairs are very likely to start spawning under these conditions.

    This is a really good sign that a fish feels safe and healthy.

    Both my friend and I keep fish that spawn to this day, which is something I’d never expect to happen from simply switching their pellets with live food.

  5. Make sure there’s enough flow in the aquarium. Sufficient flow keeps saltwater fish active as if they were in the wild.

    A good water current stimulates the fish’s muscles and keeps them toned.

    This in turn may fasten their metabolism and immune system response.

    I know a few experienced reefers who swear by having strong powerheads in their hospital fish tanks and claim that it helps fish go through disease easier.

Persistent myths about Ich control in a reef tank

I feel obligated to address the common misconceptions that relentlessly get repeated over and over again.

Most of what I’m about to discuss in this section has been inspired by my time spent in online reefing communities. The popularity of these communities makes them very influential. However, I’m a firm believer that authority obliges you to be responsible for the information you provide.

Here are a couple of myths that you need to be aware of when it comes to Ich management:

1) Myth: “Anything that doesn’t kill corals and invertebrates won’t kill Ich.”

This is one of the more popular autopilot phrases when it comes to Ich treatments.

However, that statement is, evidently, false.

There’s literally scientific, peer-reviewed proof that oxidation kills Ich Theronts.

It’s not up for debate, the studies are out there and I linked to one of them earlier.

I’m far from the first person to have success with Hydrogen Peroxide in a display aquarium with corals and invertebrates.

Will this treatment kill all of the Ich parasites in your reef tank?


Will it kill most of them and let your fish build their resistance toward marine Ich?

Without a doubt, given you do it properly.

2) Myth: “There is no such thing as an invertebrate-safe Ich treatment.”

…And this is usually followed by:

“There are only 4 known methods to treat Ich and they all require a separate hospital fish tank…”.

Needless to say, people tend to mistake the word “treatment” with the word “eradication”.

In most cases, when we get sick, we actually treat the symptoms and let our bodies deal with the disease.

At this point, you should know that a healthy, non-stressed fish will be able to fight 95% of diseases with its natural, built-in immune system.

Marine Ich is very unlikely to kill a fish that’s kept in excellent breeding conditions.

Small populations of Ich in the aquarium water are more or less the same as vaccination for the fish.

Following these thoughts, when someone asks if there’s an Ich treatment that can be carried out in a display reef tank, it’s very likely that they mean “will I be able to save my fish without harming my corals”.

The answer to that question should always be “Yes, you can either keep the parasite’s population under control or eradicate it with the help of a separate hospital fish tank.”

3) Myth: “If the white spots went away during treatment then it’s due to the life cycle of Ich.”

In one of the studies, I cited above the scientists explicitly mention that Hydrogen Peroxide was observed to force trophonts to leave their host.

Besides, let me elaborate further on why this way of thinking is often wrong.

Other studies on C. Irritans show that each Tomont cyst will release hundreds if not, thousands of free-swimming infective Theronts.

Though only between 5 and 20% of the Theronts will succeed in infecting a fish under ideal conditions, that’s still a lot.

As established earlier, Tomonts won’t all release their Theronts at the same time, in the same instant.

By doing some math you’ll see that with this pace of reproduction you should observe a growing number of white lesions on your fish during an active Ich outbreak.

This is always the case if no actions to improve the condition of a weakened fish are taken.

However, If you start the treatment and see the white spots decreasing or disappearing and not coming back in a few days then what you’re doing likely has a real impact on the ever-multiplying population of the parasite.

4) Myth: “During Ich management the tank is only one stressing event away from another outbreak.”

This one is, perhaps, true but there’s more context to it.

Saying that about Ich management is rather pointless and I personally consider it a form of needless alarmism.

There’s an inverse relationship between the success of a fish’s immune system and the stressful events going on in the reef tank.

Looking after sensitive marine fish means that they are potentially one stressor away from any disease, ever.

If your fish keep getting sick or mysteriously dying you are likely doing something wrong and they are not happy.

Water temperature fluctuations and incompatible tank mates are the first things that come to mind.

Throwing in an extra heater, being wise when choosing your new fish, and feeding live foods can go a long way in saltwater fish keeping.

The reef tanks in which my friend and I control Ich have been up and running free from parasitic outbreaks for years.

5) Myth: Each successful treatment of Ich in the display tank is an “anecdotal experience” and is, therefore, dismissed as invalid evidence for success.

There is no one study to particularly test a reef-safe treatment of Ich in marine fish.

However, there are many (I cited a couple above) suggesting that it could be done if you just connect the dots, so to speak.

There’s this tendency in online communities to bash someone if they’ve tried something unpopular and had good results with it.

People there would often claim that it was an anecdotal experience and not scientific evidence.

Experimental Ich treatments are no exception.

Don’t let me be misunderstood, I’m a big proponent of the scientific approach and all the decisions I made about my reef tank have been heavily influenced by peer-reviewed scientific papers.

On the other hand, one good example of someone with a supposedly anecdotal experience is Paul Baldassano.

Paul preaches feeding with quality live food and introducing fish infected with parasites to your reef system on purpose.

What you may be interested to know about him, however, is that he has a 100-gallon reef tank that is almost 50 years old.

Some of his fish are also 25+ years old and constantly spawning, yet he has never quarantined a new addition.

Though this alone says enough about his expertise, you could call it an anecdotal experience, right?

Some would say yes, but given the lifespan of his reef tank compared to people who religiously quarantine fish and still experience aquarium crashes I would say it’s highly unlikely.

Paul was a great inspiration for me and one of the reasons I tried treating Ich in my display reef tank.
paul baldassano's 50 year old reef tank

The almost 50 year old reef tank of Paul Baldassano

Anyway, it’s important to highlight that “anecdotal” means something not reliable, because it is based on personal accounts and not research.

For example, if 1 person reports success and the other 299 report failure you could conclude that the success was anecdotal.

Yet if 120 people report success with a similar methodology and the other 180 report failure then there’s an actual incentive to dig further and find a pattern.

During my research phase about the method I’m describing here, I found that there are quite a few reports of people successfully managing reef systems with Ich.

Though these cases were not controlled environments one could argue that the sheer number of the sample is enough by itself to suggest statistical significance and not pure luck.

Personally, I did not want to set up a hospital fish tank or tear down my 100-gallon display reef aquarium.

For one reason or another, neither of these was desirable for me.

So I conducted my own research, found another way, tested my findings, and turned out successful.

To clarify, my point here is that everyone should do their own research and not blindly follow one or two people’s advice.

Do not take one piece of evidence while stubbornly refusing to accept another, equally valid, piece of evidence.

That is, in my opinion, naive at best and with such an approach we would never advance the fish keeping hobby.

6) Myth: “In time, marine Ich would die out in a reef tank due to inbreeding.”

Some people speculate that during Ich control in a display fish tank the parasite will eventually die out due to inbreeding, provided no new strains are introduced to the system.

That’s simply not true because in its essence this parasite is a single-celled organism that reproduces asexually.

This means that each new generation is an exact copy of the previous one.

Inbreeding only happens with sexual reproduction where at least two genetic lines are involved.

Even if an error during cell division occurs it would only affect the Tomites in that particular Tomont and not the whole population.

Final words

Marine Ich could be devastating for a reef tank, but it does not have to be this way. Treating it comes down to making sure your saltwater fish are happy and well-fed which is also an excellent way to keep most parasites at bay.

Did my advice help you?

Share your experience in the comment section.

Sharing is caring!

28 thoughts on “What is the Reef-Safe Ich Treatment for Fish in a Display Tank?”

  1. In my reading on this subject, the use of carbon with H.P. is recommended to take care of any toxins or excess break down of organics. Thoughts?
    The use of chemipure blue is also mentioned, thoughts?
    Thank you.

    • Hello,

      Maybe I did not understand your question, but Hydrogen Peroxide breaks down into oxygen and water in the system. So no toxins. Excess organics should be handled by your biofilter (beneficial bacteria). However, the Peroxide “oxidizes” organics, which in this case is welcome since we want to feed our fish quite a lot during the treatment. Basically, the Peroxide will take care of the excess organics from the overfeeding, which in turn won’t overwhelm the biofilter of the reef tank.

      Hope this helps.

      Thanks for being a reader,

  2. So I’m in exactly the same position, and I like how you are addressing this. It seems to me that if we approached any human disease the same way that the reef community likes to approach this, with complete exclusion of the pest , the fish would be in a similar position as the Indians when small pox was introduced. I think it’s incredibly difficult for people who have jobs and lives outside of this hobby to maintain this level of sterility. In any case, my 80 gallon reef tank is very new and I am new to this. My blue tang and coral beauty have developed a relatively mild case if Ich. Sooooo….I dont have all of the equipment (or time) to do the recommended 72 days fallow thing. I feel like until a stressor occurred to show me the symptoms, ich was there anyway. And whose to say if I had quarantined them potentially forever, that they would have undergone the stress that would result in them actually becoming sick. I could then move the to the DT and STILL have ich because they never showed symptoms. I’m any case , I’ve started dosing the 3 percent today. I think it’s sound advice to be happy with limiting spread. Without completely quarantining. Keep them healthy and spread low. It’s a great approach. That being said, the A model isn’t available. And I would need 4 D models. The W is grossly oversized. Would that be an issue?? I didn’t even look at the demensions. It may be impossible due to size alone But, I guess I’m wondering if going over in size might over dose the tank?

    • Hello Julie,

      We’re on the same page and I completely agree with everything you’ve said.

      Use a lighter solution if the Oxydator is too big. Just use a 6% peroxide solution, instead of the recommended 12%. Two catalysts. Don’t forget to feed your tang and coral beauty well and with quality foods. This situation is absolutely manageable.



  3. I bought a couple oxydators for my 160 they put off a few bubbles to start with but after an hour or so no visable bubbles. this is second day. any hints to fix this

    • Hello,

      Is the solution inside the oxydator decreasing?

  4. I have a 55g tank with ich that started after adding a Tomini tang and now the small blue tang is starting to develop worse ich day by day. I’ve been feeding refrigerated PE mysis from the start of my tank and added some garlic to it, as well as algae wafers soaked in garlic (the Tomini is picky and only eats algae wafers). Just added two Oxydator D’s to the tank two days ago and within a day one Oxydator had released almost half the 12% peroxide and most of my corals were closed up. The other Oxydator released maybe a third of its content which seemed more normal, I made a very good effort to ensure they were both set up correctly, 1 catalyst each. Anyways, I removed the oxydator that was releasing too fast and have one oxydator in the tank. The blue tang has seemed to get very slightly more white spot and is scratching as was consistent with before the oxidator. Feeding response is great from all the fish, Tomini is eating and seems better after oxydator, more lively. My question is should I add the other oxydator back and switch it to 3% solution maybe? The corals have opened up again and seem better. Oxydator d is rated for 25 gallons that’s why I used two.

    • Hi Jim,

      That’s interesting. It should not be that the same Oxydator with the same number of catalysts releases more Peroxide than the other one. Yeah, if I were you I’d add it back and switch to 6 or 3%. Corals closing up is normal in that case, and I doubt there will be any lasting consequences for them. Keep in mind that in the first couple of days the peroxide will oxidize organics in the water and after their contents are lowered it will become more efficient in killing Ich. Corals should adjust accordingly and, also, don’t forget to lower the intensity of your lights a bit because of the increased water transparency. Other than that, your Tomini’s behavioral improvement shows that you’re going in the right direction. 🙂


  5. I’m sorry to bother you two years later, but this is totally safe for corals and shrimp right? If I just manually dump(dose x ml amount of 3% hydrogen peroxide) it will work as well? One of my fairy wrasse has ick currently. The only thing I run is chemipure blue, should I remove that?

    • Hey Brittany,

      It’s why we use it – it spares our corals and shrimp. As to effectivity – it has been my experience that for some reason manual dosing is way less effective than doing so through an Oxydator.

      Also, don’t be sorry – thank you for being here.


      • That’s helpful! I’ll look into getting one, but while I wait for it to get here, I can just plop it right in at night, just remove the chemi pure? Also, can I use the 3% standard hydrogen peroxide that I can get at Walmart in the first aid section as long as it’s just the peroxide and purified water?
        I’m just now seeing this reply, sorry!
        This is my first real successful reef tank and I don’t want to screw it up 😊

        • Hey,

          You can do manual dosing while you wait, sure! And yes, the 3% standard solution would be just fine.

          Congrats on your reef tank – you can overcome this!


          • Thank you! My fairy is struggling, I’m hoping hard this brings him back!

  6. If you are just increasing oxygen, utilizing this method, would just bubbling pure oxygen work? Or would introducing ozone work as effectively?

  7. Great work here Momchil.

    We’re in the position here of not having enough space in our flat for a quarantine tank and have got a 700l system with some v-e-r-y old fish (that are very dear friends…) that recently got a dose of itch after we brought in a new-comer. As well as feeding our fish with garlic and frozen/fresh foods several times a day we are treating the system with polylab medic twice a day (switching off all of the lights incl the UV steriliser, for at least an hour after each treatment). I am really convinced by your work to support the use of oxydators, and I’ve done some other research from other sites and forums to back it all up. Also, my partner is a member of some FB forums and it seems that more and more people are beginning to use oxydators in marine systems. Based upon your work and theirs I’ve gone and bought an A type Söchting Oxydator (it says 800l on the box) and have begun to dose the oxydator (not the tank) with 6% H202 in the main circulation pump chamber (well away from the refugium and skimmer but not in the DT – it is the chamber before the DT. I figured that as I was using Polylab too then I’d stick with 6%.

    My question is on your point about not running a UV steriliser at the same time as running an oxydator.

    Surely the 02 bubbles being released by the oxydator means that the only waste product to the process is hydrogen? I can understand not having the UV steriliser running IF I was dosing the tank with pure H202, but I’m not doing that; I’m applying a catalyst to split those molecules into their component parts to increase the overall 02 density of the water, so surely having the UV unit activated would be irrelevant? If I’m right then running both together shouldn’t be a problem – or am I missing a point here? Like, I’m no chemist but this seems logical.

    We’ve received advice from hobbyists that say it’s no problem to run them together, but I’m mindful of the degree of detail you put into your work here and I’m worried that I might be causing harm to the fish, corals and inverts, and that’s the last thing I want to do.

    Could you enlighten me as to your thinking?

    Thanks a lot

    London WC1

    • Hi Jamie,

      Thanks for your very valuable and descriptive input!

      I think I am being overcautious with that part of the article. I can assure you that if you’re not running the Oxydator right in front of the UV sterilizer’s inlet you are not putting your fish at risk. I’m still waiting for an actual chemist to chime in on that but… Since a reef tank has a very high level of organics in the water a single Oxydator should not be able to completely oxidize all of these. No tank with live animals would ever be this sterile. The level of organics acts as a “buffer” against oversterilization. I’m thinking that only in the *very unlikely* scenario of an oversterilized tank it may or may not be potentially harmful to run a UV in close proximity to an Oxydator. All in all, you should be alright. Hope this makes sense.

      Kudos for doing your own research by the way! That’s how we advance the hobby 🙂


  8. Good afternoon, I have been looking to buy Pactor GMBH (Sochting) Oxydator A in the USA, but I do not find it, where I can buy it?, thanks

    • Hi,

      I got mine from Amazon and it’s a good price + shipping times, but I also know that TheShrimpTank has them too! I haven’t compared prices though.


  9. You are a life savior for posting this article. I, like Nes am experiencing what appears to be ich in my reef tank. Also like Nes, I have been considering removing all the inverts I can catch and the few corals and treating the entire tank with a copper based medication. This was actually my wifes idea and it sounded great because we have a 300 gallon display with roughly 200 lbs of rock… I’m not chasing fish in there or draining it near empty (obviously don’t have 250 gallons of water on hand) to get fish out. until I read Nes’s reply, I was onboard with this and was going to setup a little QT tank to help keep out any more infections. It seems as if treating the tank just isn’t going to eradicate it, unless a new addition to his tank had it and brought it back, at which point I would probably fall into the same category. What space I have available I would rather have a coral grow out tank in the future, not a QT tank that isn’t used often enough.

    I had an outbreak of what I thought was ich, but apparently was velvet due to how fast it spread and how fast my fish died. I lost over 20 fish and only 2 survived (Purple Firefish and a Lemon Chromis). This was heart breaking. We went three months playing catch up on the tank and trying to get it back in good shape and letting the velvet “run its course” and we never seen a sign of velvet on the two surviving fish (or ich if it was that, either way no spots at all for three months). That’s probably not saying that the parasite died off, but running UV after dosing plenty of Ruby Reef Rally and Kick Ich Pro and I figured it would have died off. Tank was baron then other than the two troopers.

    Now I would prefer to implement this maintenance setup instead. I have a doser already and it’s not in use currently. I would like to do the 3% H2O2 dosage to my tank. If I used the dosing method instead of the oxydator, would I be able to continue this indefinitely? With how I’m understanding your approach, I would also be able to reduce the amount dosed per dose when the parasite is in check, correct? Using the doser I’m going to drill a hole in the cap of the original bottle and run the tubing in there to ensure the peroxide stays dark. The room stays dark as well probably 23 hours a day (I’m lucky enough to have a tank room behind the display tank).

    Additional questions:
    1. Will this have a negative effect on copepods? I have a decent colony of copepods currently that feed a fat Mandarin. My wife will have me sleeping on the coach if her Mandarin dies because I kill the copepods. I used hydrogen peroxide to kill algae previously and the next day or two I stopped seeing as many copepods. Maybe this was coincidence though, because I had a nutrient spike and pretty sure there was amonia in the tank from this, since I later detected nitrites. Anyway, your thoughts?

    2. I read your notes on the UV sterilizer and hydrogen peroxide being mixed probably being a bad thing. What about if I reduced the overall amount of hydrogen peroxide being dosed? Probably still not very safe is it? By my calculations I would need about 2.2 ounces of hydrogen peroxide being dosed daily for my tank volume. If that were to be reduced to .5 after the initial treatment would I be able to couple that up with the UV, or is it better to use the UV as the maintenance afterwards? Also, this is a 57 watt Aqua Ultraviolet I’m speaking of, just in case that is necessary information.

    3. Right now it’s just my Powder Brown showing signs. I’m almost certain this isn’t velvet because we had 3 months with not adding any fish and the two fish that survived never shown any signs of any infections. This Powder Brown was added a week ago and its appetite is healthy. No other fish show signs. However, I do not want to experience that sort of loss again. We have a decent stock of fish currently, so my question is (I read you found research on this) do you really think I could find success with this against velvet if it is that again? Would your dosing recommendations be the same for velvet as it would be for ich?

    4. Since posting this article, have you had to use this method on any other tanks? Have you had any success stories other than those two come to you, either through this posting or through your community?

    5. Should GFO be discontinued in addition to carbon?

    6. Should the skimmer to be turned off at all during this treatment? I would assume no since most people that treat with peroxide for other things don’t and since it’s in the water column it will likely just continue out of the skimmer, but wanted your thoughts on this.

    7. How do you know Paul Baldassano? That’s just outright amazing he has a 50 year old reef tank and doesn’t QT anything. This guy is now my idol. What a wealth of knowledge he must be! Does he have a blog or social media or anything?

    Thanks for your time and I’m looking forward to communicating with you on this.


    • Posted additional comment in error

    • Hi Todd,

      Let’s get you through this!

      Ok, let me try and answer each of your questions.

      Q: If I used the dosing method instead of the oxydator, would I be able to continue this indefinitely?

      A: Sure, you can. The advantages of the oxydator are primarily that it uses no electricity, no batteries, you don’t set up anything and there’s nothing that could go wrong as with electronics.

      Q: With how I’m understanding your approach, I would also be able to reduce the amount dosed per dose when the parasite is in check, correct?

      A: Correct.

      Q: Will this have a negative effect on copepods?

      A: I wouldn’t think so, no. It will reduce the population some, but not by much, in my opinion. For your personal peace of mind, I found a scientific study saying that a concentration of 8.5 mg*L-1 had no effect on copepod populations – https://www.facetsjournal.com/doi/10.1139/facets-2019-0011 . We need to make some calculations for this one. So mg*L-1 is the same as mg/L. 1 Mg equals 0.001 ml. One US gallon has 3.79 liters. Doing some calculations we can see that 8.5 mg*L-1 equals 0.032 ml per gallon. However, the scientists used a Hydrogen Peroxide solution of 49.5% which is 16.5 stronger than a 3% H2O2 solution. Doing further calculations we can see that this means 0.53 ml/gallon of H2O2 would be in the safe range. The study found that double that dose (1 mg/gallon) would kill roughly 14% of all adult copepods and 30% of the younger copepods. Reading further, 10 times the initial dose (5 mg/gallon) would kill roughly 34% of the younger copepods and 90% of adults. In the article, I suggest using a 12% solution as a therapeutic dose, which is 4 times stronger than a 3% one. This would mean that 1.25 ml/gallon of a 12% H2O2 solution would have the same detrimental effect on copepod populations as would 5 ml/gallon with a 3% solution. Hydrogen Peroxide efficiency also depends on the level of organics in the reef tank. A reef tank with high organics would need more H2O2 than one with lower levels of organics. Anyway, I’ve also read reports on people who dose Hydrogen Peroxide continuously without notable losses in their copepod populations. You should negotiate with your wife the possible effects of a heavy Ich infestation versus a somewhat reduced copepod population. 🙂

      Q: About using Hydrogen Peroxide and a UV sterilizer together…

      A: I honestly have no idea how safe that would be. I don’t know what happens in reef tanks when you combine these methods in practice. It could be nothing, but it could also be a disaster. In any case, if you keep up with the live food + Omega 3 diet for your fish, I think that a powerful UV sterilizer such as yours will be able to keep the Ich under control. However, if you don’t want to maintain the diet for your fish or you can’t – from what I’ve seen continuous release of Hydrogen Peroxide would likely do a better job as a preventive measure. Nevertheless, I did read a report by someone who combined UV and H2O2, but they used very little Peroxide (which would not be effective for Ich treatment, IMO). It’s really a guessing game when it comes to how much the exact oxidative potential of Hydrogen Peroxide irradiated with UV light would be…

      Q: Do you really think I could find success with this against velvet if it is that again? Would your dosing recommendations be the same for velvet as it would be for ich?

      A: I’m absolutely positive that Marine Velvet could be treated this way. I’ve done it in another tank. I did pretty much the same there. I’ve also read multiple reports on other reef keepers doing it. Reading other reports further I think that Velvet could be treated by even lower doses of Hydrogen Peroxide. Particularly 1.5-2 ml of 3% solution per 5 gallons of water. The combination of good live food and water oxidizing seems incredible at this point.

      By the way, I have articles on identifying white spots on fish if that could help: https://aquanswers.com/white-spots-on-fish-fins-gills-body-identifying/

      Q: Since posting this article, have you had to use this method on any other tanks? Have you had any success stories other than those two come to you, either through this posting or through your community?

      A: As of right now, I’ve personally been involved in this type of Ich treatment 4 times in total. And this is just my personal experience.

      Q: Should GFO be discontinued in addition to carbon?

      A: GFO is Ferric Oxide which I think can react with Hydrogen Peroxide. I would remove that, just in case.

      Q: Should the skimmer to be turned off at all during this treatment?

      A: No need. We did not turn ours off during the ich treatment.

      Q: How do you know Paul Baldassano?

      A: I’m not fortunate enough to know him personally, but he posts regularly on a famous reef keeping forum (Reef2Reef). I honestly admire the guy. You can find many golden stories and advice from him over there. He posts under the nickname Paul B.

      Hope this clears things a bit for you. Sorry if some of the answers were somewhat ambiguous. I answer to the best of my knowledge and I’m not a chemist, nor a veterinarian. I’m just really good at researching things 🙂

      Good luck with the treatment! Feel free to ask me more questions or share your thoughts and results. Actually, do share your results if you can, I’m sure everyone who got to the comment section would be interested in hearing them out!


      • Hello again,

        I started dosing the peroxide Saturday night. So far I don’t see any changes in the ich. It seems my Yellow tang actually has velvet though. So disheartening. I am going to continue dosing and see if things begin to look up, but I’m thinking the Yellow Tang will likely die. Since I’m only going into day two though, I will have to see how this plays out. Hopefully everything begins to look up.

        • Hi Todd,

          Thanks for the update, hope everything turns out fine! What the feeding regimen of the ill fish, if I may ask?

          Also, what dosage are you using? You’re going with a 3% solution, correct? Perhaps, 2 ml per 5 gallons would be adequate.


  10. I found this article fascinating and very informative, its great to see how comprehensive the research has been on this ich treatment method. After fearing my Blue and Yellow tangs are showing signs of ich I’m keen in implementing this treatment. However, I have a few of questions:

    1. In waiting for the Oxydator to arrive you manually dosed 3% Hydrogen peroxide, could you use a doser to dispense the solution?

    2.After finally getting my head around how an Oxydator works, you used 12% Hydrogen Peroxide solution. The Söchting 101 Solution that is recommended with the Oxydator you used is only 6%. I have found 11.99% solutions on amazon, which solution did you use with the Oxydator?

    2.1. You went from manually dosing a 3% solution to a 12% Hydrogen Peroxide solution, is that correct? And were there any side effects?

    3. I’m currently using Red Sea’s NO3POX4 to control my nutrient export, will this affect the Hydrogen Peroxide?

    4. Do you know if the Hydrogen Peroxide changed the PH or ALK of the water?

    Sorry for all the questions.

    • Hi Nes,

      Thank you for acknowledging my efforts! Glad to have you as a reader!

      Anyway, onto your questions:

      1. You definitely can use a doser. Keep in mind it’s best to store the Hydrogen Peroxide in a dark-colored bottle, so that little to no light “spoils” the solution. If you use a doser, just wrap up the transparent canister with something that will keep the light away.

      2. I used the 11.99% one you mentioned (I got mine off Amazon too). I did not use the Söchting one.

      2.1 you’re absolutely right! There were no side effects whatsoever. The oxydator did its job well in distributing the solution over time.

      3. I wouldn’t think so, no. For the sake of complete transparency – having fewer organics in the water could technically lead to a more potent H2O2, however, both reef tanks I describe in this article had little to no Nitrate or PO4 in the first place. I’m sure these two compounds are not the only source of organics in a reef aquarium so I wouldn’t worry about it.

      4. Good question. I remember the PH in one of the tanks I treated fell with between 0.1 and 0.2 points but that was over the course of days and after that, it remained there. Nothing to worry about, in my experience.

      No problem, ask away if you have more questions – that’s what I’m here for. 🙂

      Good luck with the Ich treatment, do incorporate the food recommendations as well as, in my experience, they solidify the results.


      • Hi Momchil,

        Thank you for answering my questions. My poor Blue tang looks quite distressed tonight, its definitely Marine Ich. I’ve ordered the recommended oxydator and H2O2 (11.99%) and will be running to the chemist tomorrow to get whatever 3% H2O2 I can get until the oxydator is delivered. I also ordered Omega 3 capsules which I will start incorporating into their food as a soon as it arrives.

        I did have some more questions that popped to mind:

        1. Did you remove any carbon from the system?

        2. You mentioned you had a refugium on the system that wasn’t affected, did you run a normal refugium light schedule? E.g. opposite light cycle to main tank lights.

        I seam to be cursed with Marine ich. I had it last year. Luckily, I didn’t have a great deal of invertebrates and just one coral. So I did what many would find unorthodox, I took out all my invertebrates and one ducan coral and placed them in a small 30Ltr tank as they were far easier to catching than fish. I then dosed my display tank with Cupramine. I did two rounds of this treatment as I think I didn’t do it for long enough first time round as the Ich came back quickly. To get rid of the Cupramine I used seachem cuprisorb and carbon. When I could test no Cu in the tank I started to add back my invertebrates. I did two ICP 3 months apart which confirmed I had no Cu in my system.

        However, this time that’s not an option, I’ve since builded up my coral collection and felt quite helpless until I read your article. Thanks!

        • Hi again, Nes.

          1. Yes, we removed the carbon media from our reef tanks both times.

          2. I switched to a daytime-only refugium schedule when dosing to H2O2 because I did not want the excess light to mess with the efficiency of the treatment during night hours (when it’s most vital because that’s when theronts are released).

          Well, it’s this time of the year again – the Ich season! Temperatures fluctuate right now and especially in our tanks. It’s why I think it’s so important to have an extra heater in the tank. When the household temperatures drop during the night (or day) it will help to offset the swing. Did the previous Ich infestation occur at the same time of year or, say, early spring? Just curious, as there may very well be the need for one extra aquarium heater!

          Anyway, this is precisely why I tested this and wrote the article – because sometimes catching fish in a large aquarium is not an option.

          Good luck and do keep me posted!

        • I also felt hopeless until reading this. I would love to know how this works out for you. I lost a lot of fish earlier in the year and do not want a repeat of that so I’m looking to employ this in hopes of saving my fish. I can’t spend a bunch of time chasing them and trying to treat them every time they show signs. I was going to do the same you did and treat the entire tank but I fear I will just see it come back another time. Good luck with this and I hope your fish are healthy soon!

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.