Here’s a scenario for you: You take care of your aquarium by the book but suddenly there’s a strange black fuzzy growth that’s now covering everything.
Scrubbing it removes the stuff for a while but it keeps coming back.
At first, it appears as black mold, often, in a freshwater aquarium environment and it later develops to a beard-like growth. It’s progressively attaching itself to plants, decor, and rockwork.
Is it there to stay?
Are black algae in the fish tank bad for aquatic life there?
After months of fighting it, I really got to know it and finally, I found the cure.
Let’s cut to the chase here.
Quick overview of what Black Beard Algae is
Despite its color, Black algae, also known as Black Beard Algae is a member of the red brush algal family in the Rhodophyta division.
In fact, in some cases, it can actually appear bluish or green-ish in coloration.
It does not only infest aquariums but also pools, ponds and other artificially-managed bodies of water.
It’s very persistent and is often difficult to remove because it has a tendency of returning.
It’s soft to the touch and appears like patches of dark hair, hence the name.
With the right approach, permanent removal of beard algae is possible, however.
Algae grazers such as the rubber lip pleco, Siamese algae eater, the American flagfish and the black molly can help immensely.
The issue, however, should be resolved at its core.
Here’s how a heavy black beard algae infestation looks like in an aquarium:
Image by: Grahms
And here’s how black algae appears inside of a pool:
How to remove black beard algae from your aquarium once and for all?
Despite being really good at exploiting nutrients, this invader has weaknesses. I’ve done my research and eventually found a couple of solutions.
They have all been tested in my or other people’s fish tanks. I am now confident to share them with you.
To get rid of the black beard algae in your aquarium for good you should:
1. Dip all of the affected decor in Hydrogen Peroxide
This can be done with a regular over the counter peroxide (3%).
This method is often used for fungi treatment on new seeds right before their germination.
Bear in mind that the more gentle plants (Japanese Moss balls being one) may take damage as well.
However, it’s worth taking the risk considering you’ll get rid of that black beard algae.
If you only have plastic plants you can even use bleach in a 1 to 20 ratio, although peroxide will work too.
Soak all the decor that is visibly affected for 2 to 3 minutes (use a timer!) and then rinse thoroughly.
The nice thing about peroxide is that it leaves virtually no residue and you can instantly put your plants and rock back in the aquarium.
I know that soaking in pure peroxide might seem a little radical, but in my experience, black algae are really hard to banish.
Simply dosing teaspoons of peroxide in your fish tank water won’t cut it.
2. Reduce phosphate (PO4) in the water
Phosphates are a byproduct of almost everything that decays in your aquarium.
This includes leftover food when you accidentally overfeed, plant and algae decay, even fish waste.
However, phosphates will also spike with the use of carbon filter media, hydrogen ion buffer solutions (pH buffers), kH buffer solutions and aquarium salts.
If these sound like way too many possible causes, know that I haven’t even revealed the main one yet.
The tap water itself.
It’s a smart move to test your tap water for PO4, which can be the hidden reason behind your aquarium algae infestation.
Black algae thrive in phosphate levels of 1 ppm and above.
If you suspect that your tap water is the issue, then you have two options:
- Find another source of water for routine water changes – Distilled or purified water with reverse osmosis (this is a guide I wrote on which one to use) will surely starve your black algae.
If you revert to this solution know that this water needs to be remineralized before adding it to the aquarium.
Purification clears all minerals – the good AND the bad.
A phosphate-free remineralizer I found, that does wonders is Seachem Equilibrium.
- Introducing phosphate absorbing media to your filter – Make sure that your filter turns your fish tank water at least 5 times per hour.
It’s worth pointing out that phosphate-rich tap water is behind 80% of the black algae problems in fish tanks (no science behind this number, I made it up to illustrate my point).
It was the reason behind my tank’s infestation.
And also the tanks of a couple of friends I helped. And three guys on a fishkeeping forum.
However, if your aquarium water tests read high PO4 and the tap water shows values below 0.25 ppm (which is considered safe) there are a few ways to lower it by eliminating the causes.
To lower phosphate levels in an aquarium you can:
- Add fast-growing floating aquarium plants – most freshwater floater plants have an enormous hunger for nutrients in the water column of your fish tank. They grow super fast and therefore need a lot of food, which includes Phosphates. I’ve got a quick list of 15 freshwater aquarium plants that you can check out.
- Replace current food – PO4 is used in the making of flake foods, but there are ones containing less phosphate. Elos is a brand that comes to mind as I know for sure that they make efforts in adding as little phosphate as possible.
- Feed your fish sparingly – uneaten food will eventually release phosphate and encourage black algae growth. Dosing meal portions is vital and you should take the number and type of fish you have into account.
- Clean the tank more often – As redundant as it may sound it’s a good idea to go one further on this one. Food and other debris are the usual suspects for phosphate build up in your water.
- Clean the filter – Filters are known to hold enough muck and residue that will eventually spike the levels of PO4.
- Opt for a carbon media with phosphate absorbers – This is for freshwater fishkeepers. Saltwater carbon filter media is often made in a way that prevents phosphate build-up.
- Review your water conditioners – These often have PO4 in them. Everything that treats water from buffers to pH alteration products contains a good amount. Do yourself a favor and research them well, before buying.
3. Feed your plants by boosting Carbon Dioxide.
Whenever the CO2 levels in your aquarium become low your aquatic plants find it hard to extract the needed amount from the surrounding Hydrogen carbonate.
Black algae, however, is really good at that and it will outcompete your plants and thrive.
When this happens your pH will elevate, which is a really good sign that a poor CO2 level is your problem.
In an aquarium low on carbon dioxide, the algae will be stiffer to the touch and even the Siamese Algae Eaters won’t bother munching on it.
By raising the CO2 levels in your aquarium you give your aquatic plants a kickstart to the competition for nutrients and the eventual starvation of the algae.
Soon after the effect takes place the BBA will become weak and therefore an attractive snack for your algae eaters.
Two stones with one bird, so to speak.
My favorite way of introducing more CO2 to a fish tank, in terms of efficiency, is with Seachem Flourish Excel (but probably so is yours, because the stuff is really good at that).
Aim for 20 to 25 ppm, granted that your Oxygen levels are in the healthy range.
Don’t forget that carbon may spike your phosphate.
4. Introduce black algae eating fish to your fish tank.
The true Siamese Algae Eaters (SAE for short) are known to feed on black algae.
There’s a catch, though.
This method should be combined with either the peroxide soak or the CO2 injection method.
Both methods will render the algae weak and soft enough for your SAEs to feast on it.
Many people I know report that after weakening the algae a sudden interest from their algae-eating tank pets occurs.
That being said, true Siamese Algae Eaters (visit the link for more info on this fish) are not your only friends when it comes to an appetite for algae.
You’ll be surprised at how diverse the reports are on what else eats black beard algae in aquarium habitats.
Most plecos should eat the stuff by definition too, with the rubber lipped ones doing it at impressive rates (link to a complete guide I wrote on those).
Here’s a full list of reported fish that will eat black algae:
- American Flagfish
- Black Molly
- True Siamese Algae Eater (young ones, as they pick the habit of feeding on the stuff)
- Chinese Algae Eater
- Twig catfish
- Bristlenose pleco
- Rubber lipped pleco
- Pigmy suckermouth
- Rosy Barb
- Cherry Barb
- Common Goldfish
The Amano shrimps are also avid black algae eaters.
Side note: Let me know in the comments if you’ve seen other fish feasting on BBA, so I can expand this list further.
I have written an extensive guide on the best algae eaters in the aquarium-hobby where you can learn more about each of the species listed above.
5. Boil it away with a heat treatment.
Algae like warm but not too warm.
This is also a very effective way of getting rid of the stuff, but you’d need to quarantine the inhabitants of your fish tank first.
Find a good temporary storage for your fish and live plants.
I had a couple of fake plants that I left inside (they were also covered in BBA). The whole procedure takes only an hour and a half.
Put your heather at 110°F to 120°F (45°C to 50°C) and wait it out.
I had algae on my live plants as well so after I removed them I dipped them in hydrogen peroxide.
The heat will burn the black algae causing it to eventually die off or get eaten by your algae eaters soon after.
My tips for extra efficiency:
1. I would not recommend using water from the fish tank in the temporary one if you’re about to execute the heat method. Some spores of the algae might still be present.
The good thing is that the removal will only last a little over an hour, so no cycling and all that is needed.
2. While you wait for the water to heat up you can add a couple of spoons of peroxide. I did a ratio of 1:150 peroxide to water.
Don’t worry, the peroxide dissolves and will not harm your fish afterward with that ratio. The algae, however, will most likely be permanently destroyed.
3. Clean the gravel before the heating. Get rid of any leftover food or fish waste.
6. Cut out the photosynthesis of the BBA.
This one could be risky if your tank is heavily planted.
Black algae need light but so do your live plants.
This is also the method that was the least efficient for me, but I feel like it’s worth mentioning.
What I did was turn off the lights for 3 days straight.
After that, I lowered the daily dose of light to about 6 hours (instead of the regular 8).
It took the algae more than a week but it did start to disappear.
However, this was not a permanent solution to my problem.
BUT if overfeeding your plants with light is the cause of your BBA issue it will work for you.
Bear in mind the light needs of your plants – if they are low to medium light plants then it would probably not damage them.
How did my fish tank get black algae in the first place?Black algae is usually introduced to an aquarium from outside sources like contaminated plants or even the guts of fish.
The truth is you will always get a few spores no matter how careful you are when you pick up new plants or fish.
But spores won’t be a problem if you don’t allow them to grow and develop.
The two main reasons for black algae outbreaks in fish tanks are:
- Imbalance of nutrients – Note that I’m saying imbalance and not just “too much”.
Insufficient CO2 in your fish tank, for example.
In that case, your plants simply can’t compete with the algae, because of inefficient photosynthesis processes.
Too much leftover food or high phosphate levels are also favorable to the algae’s growth.
- Improper lighting – Rarely aquatic plant will need over 8 hours of light.
When there’s an imbalance of the incoming light and the amount your plants actually need algae comes in the picture.
Old lights will sometimes get dim and not give off enough light for your plants.
In this case, some owners decide it’s better to just leave them on for longer instead of getting new ones. Pause reading this article here and check your lights now!
Are they dimmed? If yes, here are some proper lighting options to consider.
The link leads to a guide where I give detailed advice on how to approach your aquarium lighting in a correct manner.
Prevention of outbreaks – How to never get black algae again
If you got to this part of the article you probably have the answers to that already.
But it’s important to follow this checklist once you’ve defeated the unwelcome invader.
Black beard algae WILL take advantage of any favorable conditions.
To prevent BBA from ever coming back to your aquarium I strongly recommend that you pay attention to:
- Overfeeding – everyone can get carried away with that. I have.
After all, we do care about our pets and want them to feel good, the main part of which is being well-fed. However, excessive food is also food for algae.
Do research on the fish you have and feed them accordingly.
If you’re not confident that you will never overfeed again, I can recommend getting an automatic feeder.
Eheim offer one, that’s actually pretty reliable.
If you want to see how the device looks, Amazon has it.
There’s also the advantage of not having to worry about feeding when you’re out of town.
- High PO4 levels – You don’t want anything above 0.25 ppm in your aquarium.
- Aquarium hygiene – You are probably eye-rolling right now, as I know everyone is religious when it comes to cleaning. Still, all waste products, even in your filter can cause nutrient imbalance.
- Excessive light – Keep the lights on as much as needed but no more. Investigate your plants’ needs.
- Low CO2 levels – Carbon dioxide is vital for your live plants. With the right levels, they will be able to function properly and effectively use all other nutrients they need.
Healthy plants will outcompete any algae.
- The right equipment – Once you get rid of the intruder you can count on gear to prevent future outbreaks.
Killing algal spores before the bloom occurs is your best bet. Ultraviolet sterilizers use high-energy radiation that damages the DNA of the spores, preventing them from explosively multiplying (visit the link to learn more about that).
- Live plants from unknown sources – You could get a plant that carries black algae (though not visibly) even at a big pet store.
It’s not paranoid to run them through a light disinfection procedure before adding them to your fish tank.
Use Hydrogen peroxide and water in a 1:4 ratio and let the new plants soak for a couple of minutes. Better safe than sorry.
- Questionable pet store water – Whenever you buy a new fish, use a net and don’t just pour the water from the bag in your aquarium.
It would be even better if you quarantine them for a while before adding them to the tank. I usually wait for 24 hours.
Black algae is a menace and also one of the most stubborn algae out there. However, this does not mean we should tolerate it.
And now I have one question for you. Did my advice help you?