The 4 Best Aquarium Bacteria Supplements & Starters

Updated: 05/2021.
The main aim when cycling your new fish tank is to make sure the aquarium is habitable.

The best way to encourage this process is by introducing bottled bacteria that act as an aquarium cycle starter. If done properly the cycling will only take 2 weeks instead of the traditional 8 to 10. This is because the nitrogen cycle can be rushed with the right set of beneficial bacterial species.

The good news is that be it freshwater or saltwater, your new setup will likely benefit from a good nitrifying bacterial colony. Many of us have learned to appreciate a fast nitrogen cycle, so we dutifully supplement the aquarium with a bottle of healthy live bacteria to support its biofilter.
So what’s the best aquarium supplement that acts as a beneficial bacteria starter?

The Best Aquarium Bacteria Starters And Supplements?

Before we go through each entry, have a look at this comparison chart of the reviewed products:

Name: Recommended for:
1. Tetra SafeStart Plus A freshwater aquarium
2. Instant Ocean BIO-Spira Saltwater fish only and reef tanks
3. Nutrafin Cycle good for both fresh and saltwater aquariums
4. API Quick Start for planted fish tanks and ongoing biofilter maintenance

How effective is a nitrifying bacteria supplement depends on how quickly the strains it contains are going to establish themselves and coordinate the nitrifying process.

I will now walk you through the reviews of brands that I’ve personally used.

Here are the best beneficial bacteria starters for a home aquarium:

1. Tetra SafeStart Plus – Top Bacteria Starter for Freshwater Fish Tanks

tetra safestart plus

Click to compare pricing + see MORE photos of this product at:

Tetra SafeStart Plus is one of the most reliable bacteria starters you can find when it comes to the natural removal of ammonia and nitrites from a freshwater aquarium.

It is the best supplement for starting a colony of beneficial bacteria, but don’t buy into the claim that it instantly cycles your fish tank. That’s just too good to be true. What is probably meant here is that it immediately begins the cycling process, which goes on for two weeks before you see the final results.

You’ll need to give it about 14 days to work its way through a fish tank.

Ensure that the bottle you purchase was recently manufactured since the old stock is less effective.

For what it’s worth, Chewy and Amazon usually have a good supply of fresh stock, unlike small local fish stores.

It’s worth noting that there is ammonia in the bottle to nourish the bacteria (a very small amount). This is a good sign and it makes sense because it means that there are actual living organisms inside.

Indeed this supplement has aquatic, live nitrifying bacteria strains that normally kickstart the nitrogen cycle in aquariums, unlike some cheap industrial varieties that are derived from terrestrial strains.

Anyway, the bacteria need this accompanying ammonia to survive before your new freshwater aquarium can provide them with fish waste. For this reason, you should avoid applying any water conditioner that is going to lock the ammonia away, while cycling the fish tank with Tetra SafeStart+.

Ammonia detoxifiers convert ammonia into ammonium because the latter is harmless to fish. However, studies have suggested that beneficial Ammonia-oxidizing bacteria feed on ammonia (NH3) and not Ammonium (NH4+).

Good dechlorinators such as Prime have ammonia-detoxifying properties.

Now, obviously, the aquarium water should not contain chlorine since it kills these bacteria (and fish). Thus if your tap water has chlorine or chloramine, you have to dechlorinate it with something like Prime and wait at least 24 hours before applying Tetra SafeStart Plus to it. Doing so will help the bacteria starter to properly kickstart the nitrogen cycle.

You could also dechlorinate tap water by boiling it, but that takes way too long to be feasible.

Anyway, for better cycling results, start by shaking the Tetra SafeStart bottle.

Then pour in the whole bottle or at least twice the recommended dose.

In fact, I advise you to keep a second bottle at hand and apply that if there’s an unexpected ammonia spike, just in case.

After all, these are beneficial bacteria, so there is no harm in having as much of them as possible when cycling a new freshwater fish tank. It’s more important to have enough beneficial bacteria than too few.

When I use it, I usually pour in the whole 1.69 Oz bottle to cycle aquariums of up to 40 gallons.

Remember that you should only do a water change after two weeks since if you do it sooner, you risk disrupting the bacterial ecosystem. The said ecosystem is actually the balance between all kinds of bacteria, not just the beneficial nitrifiers.

Follow the aforementioned simple guidelines, and Tetra SafeStart+ is going to be one of your best bets as a freshwater aquarium bacteria starter.

  • The bacteria form colonies and start to multiply as soon as you apply this product to the fish tank.
  • One bottle of Tetra SafeStart Plus is enough to establish the bacteria.
  • It is highly effective and you can expect a fully cycled aquarium in 2 weeks.
  • Using it is a no-brainer since you just add it to the fish tank’s water and wait.
  • You can also do fish-in cycles if you add 1 SMALL fish per 10 gallons of aquarium water
  • Cannot be used for starting saltwater aquariums.

2. Instant Ocean BIO-Spira – Best for Saltwater FO & Coral Reef Aquariums

instant ocean bio spira
Click here to see the current price + more photos on Amazon.

I consider Instant Ocean’s saltwater bacteria starter to be the best option for speeding up the development of beneficial nitrifying bacteria in new marine aquariums. If you’re too impatient to wait for the nitrogen cycle to naturally establish itself you will likely benefit from using BIO-Spira.

When it comes to accelerating the nitrogen cycle in a saltwater fish tank, Bio-Spira is my go-to.

It also works fantastically for maintaining the biofilter in established Fish-Only (FO) and coral reef aquariums.

I’d also recommend using BIO Spira if you want quick results following a medication that has wiped out your biofilter, large water changes, or after adding live rock in order to populate it faster.

BIO-Spira’s live aquarium bacteria starter comes in a well-sealed bottle with a decent shelf-life. Still, you should make sure to acquire the most recently manufactured bottle.

Anyhow, what I can confidently affirm is that after 3 to 5 days of adding this product and supplying the aquarium with ammonia for feeding purposes, your test kit will read 0 ppm for ammonia.

Moreover, the nitrite level in the aquarium water will go down considerably about a week after that.

You can also use Instant Ocean’s beneficial bacteria supplement when adding new marine fish to the tank, which helps in making up for the increased bioload.

Provided the product is not an old stock and it has been maintained at the right temperature, the 3.38 Oz bottle can treat a 30-gallon saltwater tank.

However, I usually double the recommended dose to speed things up.

A storage tip: High temperature can either kill the bacteria or significantly weaken the effect of the supplement. With its shelf-stable formula, you do not have to refrigerate it as it preserves itself.

Store it at room temperature for squeezing its maximal potential.

Anyway, the product is a combination of more than one species of beneficial bacteria, being made up of Nitrosomonas, Nitrospira, Nitrococcus, and Nitrosospira, which are all alive and healthy before opening the bottle.

All these strains work to ensure that Bio-Spira is always numbered with the best nitrifying bacteria for efficiently starting your new saltwater reef tank.

  • The combination of various beneficial bacteria guarantees a fast cycling process.
  • It is not make the water in your fish tank cloudy.
  • It prevents the New Tank Syndrome.
  • Is specifically designed for saltwater aquarium use.

3. Nutrafin Cycle Biological Supplement – Good for Starting Both Saltwater and Freshwater Tanks

nutrafin cycle
Click here to see the current price + more photos on Amazon.

Due to the high concentration of beneficial bacteria per bottle of Nutrafin Cycle, the cycling process is reduced to slightly over a week whereas a natural approach would take more than a month.

As soon as you pour it into the fish tank, the bacteria begin to break down the ammonia and nitrite.

However, it is harmless to your plants, fish, and other tank inhabitants which makes it a good choice for a fish-in cycle in a planted tank.

Anyhow, while Nutrafin’s Cycle has live bacteria in it, its shelf life is actually quite long, thanks to what the manufacturer calls “bio-floc technology”. This technology preserves its stability in the long run, which I found to be true.

This is actually convenient because you do not necessarily need to look for the most recently manufactured bottle.

One thing I especially like about “Cycle” is that it is reasonably priced, so it will favor your needs if you are on a budget.

Always check the price on online shops and compare it with your local pet stores before deciding where to buy. In my experience, the physical pet stores occasionally double the price for no good reason.

The NutraFin Cycle Biological Water Supplement is designed for both freshwater and saltwater aquariums.

What I would recommend with this bacteria starter is to shake the bottle REALLY well before use. Other than that, my experience with it has been that it works perfectly fine and it does the job.

So whether you are just a novice or a star-studded veteran in fish-keeping, NutraFin Cycle is going to make things easier for you during tank cycling.

  • It has a relatively long shelf life.
  • It can be used in both saltwater and freshwater aquariums.
  • It speeds up the cycling process significantly.
  • It is affordable.
  • It is highly concentrated, so one bottle can serve a tank as large as 500 gallons (you can still use more than the recommended dosage though).
  • You always need to shake the bottle hard before use. If you forget this step the product may not prove as efficient.

4. API Quick Start Nitrifying Bacteria – For New Planted Tanks and Ongoing Maintenance

api quick start

Click to compare pricing + see MORE photos of this product at:

The API company has been in the fish-keeping industry for many years.

I use this particular product of theirs routinely.

I consider API Quick Start to be the best supplement of beneficial nitrifying bacteria for ongoing aquarium maintenance. It reduces ammonia levels really quickly when adding new fish to established freshwater fish tanks.

It is usually during such maintenance (like a filter change, the addition of new fish, etc.) that some fish die or fall sick due to ammonia and nitrite build-up.

With a bottle of this aquarium bacteria starter, you won’t worry about what to do with a dead fish that’s floating in the tank or a sick one spiraling while leaning on its side.

When used for starting the nitrogen cycle, these live, nitrifying bacteria initiate their ammonia-oxidizing processes immediately after you pour the liquid into the aquarium.

My experience has been that it won’t take long (read not more than 14 days) before the aquarium water is conducive for new fish.

Unlike Tetra SafeStart+, which virtually skips the build-up of nitrite, API Quick Start forces the nitrogen cycle through its natural course.

This means that you will observe a nitrite spike right after the ammonia one.

For this reason, I consider API Quick Start to be the best nitrifying bacteria starter for cycling a new, planted fish tank, where the aquatic plants will take care of the nitrite spike.

It’s a well-known fact that live aquatic plants prefer ammonia and nitrIte over nitrAtes for nutrition.

With API Quick Start you’ll both speed up the cycling of the planted aquarium and feed your live plants in the process.

Note that you can still dose aquatic plant fertilizers to the aquarium during cycling with this bacteria starter.

Though this happens rarely, during the application, the water in your fish tank may turn cloudy, but this is not going to last long.

Anyway, API Quick Start is compatible with both saltwater and freshwater aquariums.

To cycle a saltwater tank you just double the recommended dose for freshwater aquariums.

Though I like Quick Start, I’d still use BIO-Spira for starting a marine tank.

Anyway, this API’s bacteria starter requires no refrigeration though you should ensure that it is always in a cool temperature condition.

The optimal storage temperature is 40°F – 80°F (5°C – 25°C).

Needless to say, temperatures beyond this range could weaken or kill the live nitrifying bacteria inside the bottle.

Finally, note that Quick Start’s effectiveness is subject to the correct application.

Related AQUAnswers Article: Tetra SafeStart VS API Quick Start – Which is Better and How to Use Them

  • Prevents waste-related fish deaths or ailment.
  • Enables you to add fish into your new tank sooner than later.
  • It can be used in either a saltwater or a freshwater tank.
  • It requires no refrigeration.
  • Does a fantastic job at cycling planted tanks.
  • It is not as quick as advertised, as it takes around 2 weeks before fully cycling your fish tank.

A Complete Beginner’s Guide to Aquarium Bacteria Starters

There are crucial factors you need to bear in mind as you go about choosing the most effective beneficial bacteria for your aquarium.

The following is a complete guide to aquarium bacteria starters for beginners:

1. Employing the Right Set of Beneficial Bacteria

I’ve done a lot of research to make sure that each bacteria supplement listed above contains what it should to kick-start the nitrogen cycle in an aquarium.

My research on the subject showed using the wrong bacteria could be a fruitless endeavor. Also, I’ve used the bottles myself when starting my own fish tanks or those of clients. Though I used to be an old-fashioned “do it the natural” guy, I’m now glad I’ve tried these products because by doing so I’ve managed to speed things up dramatically.

Here is why choosing the right set of beneficial bacteria is vital:

The nitrogen cycle requires more than one set of beneficial bacteria.

Therefore, a formidable bottle of beneficial bacteria should have at least two distinct strains: one that breaks down ammonia into nitrite and the other that converts this into nitrate.

One of the most well-known of these strains is Nitrosomonas, which feeds on ammonia and then produces nitrite as a byproduct. How fast this conversion occurs depends on the population of the bacterial colony.

Nitrobacter is another set of bacteria specialized in converting nitrite (NO2-) into nitrate (NO3-).

Some other beneficial bacteria involved in biological filtration are Nitrospira, Nitrococcus, and Nitrosospira.

Some brands of bacteria starters do not disclose the strains they use on the bottle.

The smaller companies may find it cheaper to employ terrestrial strains, which outcompete the actual aquatic bacteria and then die out.

This sends a user into a vicious circle of continuously adding these products to the aquarium because otherwise, the nitrogen cycle would crash.

2. Add Beneficial Bacteria Whenever There’s An Increase In Bioload Compared To Bacterial Biomass

The aquarium’s cycling rate depends mainly on the bioload versus the bacteria population or biomass.

This means that you always need to strike the right balance between the two variables if you are to see significant results in maintaining a cycled fish tank.

How often you use a bacteria supplement in an aquarium is determined by the following:

Every time you add a new fish to the aquarium, it follows that the produced ammonia amount is also going to increase.

You need to add more bottled bacteria to reinforce the ongoing nitrogen cycle.

Also, beneficial nitrifying bacteria mainly harbor surfaces.

Whenever you remove an old filter media to replace it with a new one, the old one goes with all the bacteria that are clinging to it because you cannot physically detach them.

This effectively reduces the population of beneficial bacteria in the aquarium.

Therefore, you can replenish the bacterial biomass by dosing a bottle of your chosen aquarium bacteria starter.

The same rule applies when you vacuum the substrate or change decor since the tank loses beneficial nitrifiers in the process.

In short, always watch out for any addition to (or subtraction from) the aquarium that is going to alter the ratio between the bacterial biomass and the fish bioload.

3. Seek For Freshly-Manufactured Bottles

Since these bacteria are living things, each has a lifespan like any other creature.

So the more an unused bacteria supplement bottle stays on the shelf, the more the curve flattens until it eventually loses its stamina.

That’s why you should prefer recently-stocked bottles over the overstayed ones.

If you can’t find fresh ones at your local fish store, you should consider buying online, preferably from Chewy or Amazon, where, in my experience, the stock is always recent.

4. Always Have a Test Kit Around

You do not have to wait until you see a sick or dead fish to realize all is not well in your aquarium.

As a precaution, you should be doing periodic water testing to check if the ammonia or nitrite levels are high, in which case you need to add more beneficial bacteria to accelerate the conversion rate.

The ammonia level should never be above 0.25 PPM, otherwise, your fish’s life would be at risk. A fully cycled aquarium reads 0 ppm of ammonia, 0 ppm of nitrate, and 10 or more ppm of nitrate.

Even when you are just starting a new aquarium, you need to be testing the ammonia and nitrite levels as you carry out the cycling procedure before adding the fish.

Test strips only give a rough idea of your aquarium’s water parameters.

Liquid test kits are reliable and very efficient in accurately measuring ammonia, nitrite, and nitrate.

In case you’re new to fish keeping I should probably recommend a good liquid test kit.

The Master Test Kit from API seems to be an excellent option, and many seem to agree.

You can check it out on Chewy here or on Amazon here.

One practice I usually recommend to my friends who just start out in the hobby is to have an Ammonia Alert sensor in their fish tanks (after the nitrogen cycle has been established).

Though it sounds fancy it’s actually a really inexpensive and passive method of keeping you up to date with the ammonia levels in the aquarium. A must-have!

However, a liquid test will always be more accurate than the Ammonia Alert, so don’t count solely on the latter.

5. Check The Shipping or Storage Temperature

Extreme temperature ends up weakening or killing beneficial aquarium bacteria in bottles so whether you are buying from a local store or online, take the time to ascertain that it has been kept at the right temperature.

If it is not damaged by high heat, buy it and continue to keep it at that temperature until you are ready to use it. Ordering from a reputable seller online like the ones I mentioned above is always a good strategy.


The best thing about beneficial bacteria starters is that once you introduce them into the fish aquarium, you can sit back as they quickly take charge of the cycling process.

That gives you time to go about personal matters, only coming back to test the water for its ammonia, nitrite, or nitrate levels.

If you go the traditional way, you can’t be so sure how long you are going to wait for the cycling process to complete.

Drop me a comment if there’s anything at all you’d like to ask.

Sharing is caring!

10 thoughts on “The 4 Best Aquarium Bacteria Supplements & Starters”

  1. Very informative article. This Tetra can help significantly shorten the wait time between putting water into my new tank and then placing the fish into it. What used to take a couple of weeks to a month will become a week at the most.

    • Hi Farris,

      Thanks for sharing your experience.

      When I do it, it usually takes 2 weeks to a fully cycled tank.


  2. Hi there, any thoughts on Aquavitro seed? I bought it because I couldn’t find any bigger bottle of API quick start than the tiny ones (but I’m starting with that). I keep seeing people bashing Seachems stability, so I stayed away from that, but now I realize Aquavitro is the same seachem brand just a little different. Might I achieve the same results as using just the quick start or tetra safe start? (In terms of kick-starting a safer cycling of a new 10gal tank?)

    • Hi Allison,

      I don’t have experience with that product, unfortunately. In my opinion, TSS+, and API QuickStart will likely yield the best and fastest results for your 10-gallon aquarium.

      Just a quick question – did you try ordering a bottle online?

      Thanks for the info

  3. I’m about to start cycling a 130L (34.3 gal) tank. I’ve got some media from my LFS to help. I also bought some Fluval cycle. What are your thoughts on this product?

    • Hi,

      I don’t have personal experience with it, but there was a commenter on my other post about API Quickstart vs Tetra SafeStart, who reported that he was unable to cycle his tank with it. I advised him to try TSS and he reported back with almost instantaneous improvement in his fish tank. It’s the only anecdotal experience with that product that I can tell you.

      I hope this helps.

  4. Can you help? I just purchased a Biorb 60liter Cube which uses bacterial additive to start tank. For water changers, can I use the API Quick Start or will the different types of bacteria conflict?

    • Hi Lee,

      Fair question.

      Ideally, both bottles should contain the same Nitrosomonas strains but you can’t be sure if there’s no info on the label of the BioCube bacterial additive. Just to clarify Nitrosomonas is a genus of bacteria, which means that there are several Nitrosomonas strains and not just one. It’s fine as long as it’s all Nitrosomonas and not, say, Nitrospira.

      Anyway, with this limited info, I’d suggest playing it safe and sticking to the API brand only. Then again if there’s info on the label of the bacterial additive that came with the tank and it says it contains Nitrosomonas you can combine them.

      IF the tank has already been cycled, then you can use whatever you’d like with the water changes.

      Hope this helps!

  5. Can bare floor aquariums sustain enough beneficial bacteria? The one in questiin holds 38 litres. Does biomedia HAVE to be encapsulated within a filter? Would putting biomedia in filter bags on the bare floor aquarium suffice? Or should aquarium gravel be utilised? Thanks 😊

    • Hi Lynne,

      That’s a valid question, so thanks for asking!

      Generally, the more surface area – the better.

      It does not matter where it is stored. You can literally toss a bag of biomedia on the aquarium floor and still ripe the benefits.

      Filters are usually used because they provide extra space for porous media, that you would not otherwise want in your aquarium (not aesthetically pleasing etc).

      A porous substrate just provides MORE area for beneficial nitrifiers than a bare bottom.

      This does not mean, however, that it’s mandatory for keeping a fish tank cycled.

      Hope this helps!

      Ask away if you need more answers!

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