Do (and How) They Work – API Quick Start VS Tetra SafeStart?

api quick start vs tetra safestart header

There’s an ongoing debate among fishkeepers about whether Tetra’s SafeStart and API’s Quick Start even work.

IF they do, which one is more efficient?

What is the difference between Tetra SafeStart and Tetra SafeStart Plus anyway?

Starting a new tank can be stressful for both you and your new fish buddies.

The logic behind these products is solid, but that’s in theory.

Is there a safe dose or an overdose?

Should you do a fishless cycle?

What’s the reality? The good news is I have tested them both…twice.

I’d be more than happy to show you my results and point you in the right direction.

Shall we?

Which one to choose if any – API Quick Start versus Tetra SafeStart?

Both products claim to have live nitrifying bacteria that will speed up or reinforce your nitrogen cycle.

They contain two sets of bacteria stains – one that turns the ammonia into nitrites and one that turns said nitrites into harmless nitrates.

Here’s the truth about the Tetra SafeStart vs API Quick Start comparison:

Both Tetra Safe Start and API Quick Start will work, given that they are applied in a correct manner. The cycling of a new tank will speed up significantly but it won’t happen overnight.

You can realistically expect a fully cycled tank at the end of the second week (10 to 14 days) after application. Dosage plays a major role in success.

However, following the instructions on the back is not something that will help, as they are pretty vague.

It is rather inconvenient that the instructions on both are not helpful.

After experimenting hard I’ve managed to highlight what strengthens your chance for success, eventually finding a process that, in my opinion, is foolproof.

I ran two tests on both before actually using them in a real fish tank project.

The only disappointing part is that they will not cycle your fish tank the same day.

Also by “add fish instantly” they don’t mean all of your fish.

How to use them and make them work?

After running a couple of tests I am confident to share my success formula with you.

Going through hundreds of forum threads and speaking with fishkeepers I know, I did find confirmations of my findings.

This means that my logic was correct.

Firstly you’d need to get the right bottle of bacteria.

Safe Start and Quick Start both contain live bacteria.

Both brands are claiming no refrigeration is needed.

The perfect temperature for the bacteria’s shelf and in-water life would be between 40°F and 80°F (5°C to 25°C).

Going beneath or above that range may spoil it, by killing the microorganisms and rendering the product useless.

Trusting your local fish store is okay, but I do prefer getting mine over or Amazon (link to them, that will open in a new tab). For the record, Chewy is an online store that specializes in pet supplies, so they really know how to ship the bottled bacteria properly and in the right conditions.

Anyway, if you do insist on getting from your local market make sure that they were safely stored and aim to get the most recently shipped ones (with the farthest expiration date).

Some instructions before you start are:

  • Get a bottle that has been manufactured as recently as possible – The newer the bottle, the better. Also, get at least two bottles, I will explain why later.
  • Choose a bottle meant for a larger aquarium than yours – For me, it worked best when I used the 3.38 Oz bottle of Tetra SafeStart Plus for my 20 gallons, and also when I doubled the dose recommended for the API Quick Start.
  • Make sure the ammonia is not already deadly high – everything above 2.5 ppm of ammonia will be harmful to your fish AND the bacteria. Before you start with the nitrogen cycle you need the ammonia lowered as much as possible.

With that out of the way, you can start cycling your aquarium.

Follow these exact steps to properly use Tetra SafeStart or API Quick Start:

  1. Dechlorinate your water no less than 24 hours before adding the bacteria.

    Use a dechlorinator.

    Leave the filters running during that time.

    Chlorine will kill the not well-established cycling bacteria.

  2. Shake the bottle of bacteria hard.

    This part is really important.

    Shake the bottle really well before adding the bacteria.

  3. Pour in double the recommended dosage.

    For Tetra users just add the WHOLE bottle of bacteria to your aquarium.

    Add it all.

    It’s beneficial bacteria. The more the better.

  4. Add 1 SMALL fish per 10 gallons of water.

    This should be done shortly after you’ve poured in the bacteria, within a maximum of 2 hours.

    The proportion is what worked best for me.

    By definition, this is where most people make a mistake.

    Adding a fish per 10 gallons of water is the safest way of controlling the ammonia levels.

    It’s true that you can stock the tank up, but you’d need very clean fish (ones that do not poop as much) and you’d have to feed them very carefully to either not overfeed (leaving extra ammonia work for your bacteria) or starve them (being too cautious not to overload your tank with ammonia).

  5. Feed your fish every other day.

    Test your water frequently, if you notice a spike in ammonia it’s okay to not feed your fish that day.

    Many fish can survive more than a week without food, so they will be fine.

  6. Don’t do water changes until the 14th day.

    If and only if the ammonia starts rising for no apparent reason you can do a water change to lower the levels down.

    Add another bottle of the product if that happens.

    This is why I told you to get a second bottle.

    However, there’s a solid reason behind this point.

    You’re probably using chlorinated tap water for your fish tank. In order to perform a water change you’d need to dechlorinate the water first, right?

    Water facilities in the more developed cities use Chloramine instead of Chlorine for disinfection.

    Chloramine represents the chemical bond of chlorine + ammonia.

    Seachem Prime (a commonly used dechlorinator), for example, breaks down chloramine to chlorine and ammonia, takes care of the chlorine, and detoxifies the released ammonia.

    Every product that claims to detoxify ammonia likely transforms it into ammoniUM.

    Ammonium is harmless to bacteria and fish alike, but the detoxifying effect only lasts for 24 to 48 hours.

    After that, the ammonium turns back into ammonia, which means you now have more of the latter in the cycling aquarium.

    The more Chloramine your water facility uses, the more the released ammonia after the effect of the dechlorinator expires. This could consequently harm your bacterial biofilter and fish if the contents turn out to be too high to handle.

    Author’s note: This only affects new aquariums that do not have an established colony of nitrifying bacteria.

    Anyway, another argument for not changing the water in the first 14 days of cycling (unless there’s a dangerous ammonia spike out of nowhere) is that studies suggest that nitrifying bacteria use ammonia instead of ammonium for their source of energy.

    Continuously using a dechlorinator that turns ammonia into ammonium could actually slow down the nitrogen cycle in your aquarium even further. The nitrifying bacteria would not be interested in the latter and will not be stimulated to multiply further.

    This can easily turn into a vicious circle and a never-ending supply of Prime for a new, non-cycled fish tank…

    If you’re using bottled bacteria you’d want your fish tank to cycle as soon as possible, right?

    Tip: The best way to avoid all of this is by having a separate batch of dechlorinated water to use for water changes during aquarium cycling. The “emergency batch” should be dechlorinated at least 24 hours before use. Add a little bit of bottled bacteria to it to make up for the residual ammonia and it’s good to go.

    Suggested Read: How Aquarium Fish could Die After a Large Water Change

    Despite the described scenario Seachem’s Prime still remains a fantastic option for water dechlorination in a fully cycled aquarium. I’d recommend it to anyone who is using tap water for water changes. The residual ammonia from breaking down the Chloramine would be negligible to the already-established bacterial colony in a mature tank.

    Anyway, after 14 days of cycling, you can perform a water change the regular way.

  7. Don’t test the water for the first 2 days.

    It’s okay to test it whenever you want but that is something that I stuck to throughout my tests.

  8. Turn the UV lights off for the first day or two.

    Ultraviolet light does affect the bacteria in a negative way.

    For it to successfully establish I’d strongly recommend not turning those lights on the first day after the application.

Keeping the fish tank cycled

After the second week you can gradually add fish, but of course, don’t add 10 at a time.

When doing the first water change the ammonia will go up, as there is ammonia in tap water, but I wouldn’t worry about it that much.

The levels should be quickly back to normal within the next 12 hours or so.

Don’t freak out if you don’t see your nitrites spike when water testing.

If you’re using Tetra’s SafeStart the process will skip the nitrites building up and will directly build into nitrates.

Don’t worry if your aquarium becomes cloudy at first.

The water will get clear within two to three days or a week at most.

Seeing cloudy water in a new aquarium at the beginning of its Nitrogen cycling is completely normal and it means that different bacteria are establishing their hierarchy.

Visit the link if you’d like to understand the process in depth. Understanding aquarium microfauna is, in my opinion, a core component of long-term success in fish keeping.

And that’s not an overstatement.

Which one should you choose? What’s the difference?

This is not one of those posts where I discuss the pros and cons of both products and leave the choice to you.

I have a statement:

Both can be (successfully) used for a start but If you’re starting a brand new empty tank and want to establish an ammonia safe environment I’d recommend using Tetra SafeStart.

If you’re starting a brand new planted tank, doing huge water changes, or adding a lot of fish at once to an already cycled planted tank I’d go for API Quick Start.

Tetra’s better at handling the nitrites (it virtually skips them) and API will normalize your ammonia levels quicker which, in an ongoing aquarium, is more important.

High ammonia levels may result in your fish staying at the bottom of the tank seemingly gasping in despair (click the link for an in-depth explanation of this behavior in Bettas).

The API Quick Start is more efficient when you have a planted tank as it does not handle the nitrite levels as well as Tetra’s SafeStart. Live aquatic plants prefer ammonia and nitrite over nitrate as their source of nitrogen so, by using API’s product you will both speed up the cycle and let your plants feed on the nitrite.

Note: Between Tetra SafeStart and Tetra SafeStart Plus the difference is only in the concentration of the bacteria. I’m really happy with Using the Plus version, so the instructions will remain the same.

The saltwater alternative is called Bio Spira.

API doesn’t have a saltwater version, you just double the dose.

What’s with the mixed opinions then?

Honestly, it’s probably a human error.

Seeing how (upon proper use) the products kept proving themselves to me and others I spoke to, I can only conclude that.

Then again, the negative reviews pushed me to test them myself, before anything.


Fishkeeping is a patient hobby.

Whether you choose to go natural or use bottled bacteria products for starting a new fish tank, you will have to wait it out a bit.

There is no shortcut for that, there are only shorter cuts…

Tell me how things unfolded for your new aquarium in the comments.

Sharing is caring!

344 thoughts on “Do (and How) They Work – API Quick Start VS Tetra SafeStart?”

  1. Hi,
    Thanks for your awesome article! I love how clearly you share your knowledge and experience. It’s great for people like me, who want to know absolutely everything so normally articles raise more questions than they answer. Yours don’t give this issue!
    I’ve recently started up a new 160L tank to transfer my 2 small goldfish to. (background: got a fish before I had a tank, bought 25L tank. Added gravel, plants and air stone. Week later added a 2nd, smaller goldfish because he needed a friend… After the second fish, I started reading up more and more to make sure I was giving them the best care. Which I wasn’t. Made adjustments and bought a bunch of stuff, but with the small water volume I just couldn’t get the cycle sorted anymore. This got me to a week ago when my new tank arrived and I added black flourite sand, plants and fluval u4 filter.)
    In any case, I added 2 small nerites to the tank about 3-4 days ago to add some bioload and make sure algae doesn’t start. I added the recommended amount of API quick start on the second day of the filter running. And then some more a day or 2 after, and again some yesterday after a 10% water change and some plant maintance + adding tropica’s cheap co2 system (cannot afford proper co2 injection and most of my plants are easy care, along with my LED light being low light).
    That evening (last night), is when I read your article and clarified a lot of information. About the new tank, and also the small one they’re in now which I have been using Prime for during the daily water changes, and thus shooting myself in the foot.
    The only questions I have are as follows:
    When using API as per your article, do I dose daily, or just once? I won’t do any more water changes from now until the cycle is established.
    Will the nerites keep the bacteria going for another 2-3 weeks? I need my plants to root down well before the first goldfish gets moved over (I’m moving the smaller one over 7 days before the second so that the bacteria can adjust and also because she then has a chance to grow to a more similar size as the other fish. She is also the least destructive out of the two for my plants) because, with them being goldfish, they love to uproot and munch on my plants so they need time to grow and get established before that.

    I also have a larger nerite in the small tank because I get quite a lot of diatoms in that tank, and was considering moving him to the new tank as well. I am also considering getting some cheap cherry shrimp for the big tank because their bioload is negligible (from what I’ve read) and they can hide from the fish in the plants later down the line. It wouldn’t be the worst thing if that doesn’t work, because I can set up the smaller tank for the shrimp and as a plant grow tank once the fish are transferred and the tank cleaned. Would this be alright?

    For reference, my readings over the last 4 days are:
    (nitrate comes out of the tap at 5-10 when I tested untreated tap water. Also no ammonia in our tap water).
    pH 7.6 high pH 7.4 ammonia 0 nitrite 0 nitrate 5
    pH 7.6 high pH 7.4 ammonia 0 nitrite 0 nitrate 5
    pH 7.2 ammonia 0.25 nitrite 0 nitrate 5
    pH 7.2 ammonia 0.25 nitrite 0 nitrate 5

    Thanks again for your article, and any help you can offer! Sorry for the long post…

    • Hi there Laura,

      Thanks for the compliments and thanks for being a reader.

      Let me try and answer the “only” questions you have 🙂

      1. You dose it once in the beginning and save another double dose for emergencies, such as the ammonia rising after 7-8 days (which should not happen).

      2. Nerites will keep some of the bacteria. The bacteria’s natural response is to adjust their numbers to the amount of available food (ammonia). There will be an adjustment period after you add fish. Also, kudos for doing your research and deciding to add your goldfishes one by one.

      On a side note, I’m literally in the process of writing an article that discusses plants for goldfish… You could give it a read when it comes out these days. Anyway…

      3. I’d say move the larger Nerite to the new tank. Typically, diatoms kind of sort themselves out with time.

      4. Goldfish are primarily herbivorous but they still remain opportunistic omnivores (as you’re probably aware as an owner). They may or may not try to snack on the shrimp. If it’s not too much of a hassle you can drop a shrimp or 2 in the tank with the goldfish and see how that works out (after the tank has cycled). If your goldies decide they’re not interested in going on a rampage with the shrimp then you may even see the cherries breeding. There’s another scenario where the adult shrimp fend for themselves well, but the goldies eat their babies. My point is – it will be pretty much trial and error for you.

      Four days is still early but you have cool readings. They mean the nerites are producing enough waste to start the ammonia-oxidizing bacteria. Also, the drop in pH means there are SOME strains of bacteria at work.

      Anyway, I hope this helps.

      Shoot me up another comment if you have more questions or if you just want to keep me and other readers posted with your progress.


  2. Hi im back. Hope you have been well
    To everyone still reading this….It works! ive used this method to set up a 55litre and a 125 litre with no issue. Im only back to check what the dosage would be for my 315L.
    would it still be a full bottle only or maybe 1.5?

    im also gonna be using an fx4 external filter. hopefully all is still as written.

    • Hi KA,

      Thanks so much for getting back to us – I’m sure my readers will be happy to read your feedback.

      I’d use a bottle and a half. 315 L is around 80 gallons, and the bottle says it treats up to 100 gallons, so I’d be on the safe side if I wanted a fully cycled tank in 2 weeks.

      Anyhow, the FX4 is perfect for an 80-gallon tank, it will let you stock a lot of messy fish if you want.

      Good luck, KA


  3. I have 9 small Coldwater fish in my 40 gallon tank i did not start the cycle. Should i wait till the ammonia from the fish waste and food is at a certain ppm before adding the tetra safestart plus so the bacteria has food to eat? Or should i just keep putting a bottle a week in the tank with the fish?

    • Hi,

      Despite there being no ammonia yet, you should NOT wait because the fish WILL produce waste and it’s just a matter of time before the levels rise.

      In fact, it should be your top priority not to let the ammonia spike.

      Following these thoughts, add the bottle as soon as possible – the bacteria will adjust their numbers according to the available ammonia.


  4. We are seeing between .25 and .5 ammonia today, day 8 of new 5 gallon tank with Betta in. Wanting to lower it of course…we’ve been adding double dose of api quick start since day 1, do we keep adding the bacteria every day until day 14? I have 2 gallons of tap water with dechlorinator added this morning ready to use tomorrow morning to lower ammonia. What else do we need to do?
    Also, today our 2 betta bulbs looked awful so I trimmed the brown leaves down to the base and added half a flourish tab to the base of each one in the gravel.
    This is an 8 day old tank so I know we have to keep an eye on it. So far fish is showing no signs of stress, ph is 6.8-7.3 depending on brand of strip we use. Lol

  5. Hi, I followed your instructions to cycle my 10 gallon tank using tetra safestart plus, used the bigger bottle, I’m on day 14 and have been testing the water daily with the api master kit for PH, nitrite, Nitrate and Ammonia every other Levels were all 0ppm by day 11, with the exception of nitrates which were showing 5ppm. Day 12 my Ammonia went up to .25ppm and today (day 14) Ammonia is closer In color to .5ppm, nitrite 0ppm, ph 7.2, and Nitrate between 5ppm and 10ppm. Is this Ammonia spike normal?

    Was planning on vacuuming the gravel as I can see bits of old food stuck in there and then add some new water(already have some conditioned and will be ready tomorrow)also would add a small bottle of TSSplus.

    What are your opinions and suggestions?
    Thanks in advance!

    • Hi Jordan,

      Yes, what you’re describing is unusual. Your tank was cycled before that so there’s something contaminating it. I was about to guess that there may have been some leftover food on the bottom of your tank but you said it yourself. I would recommend just vacuuming the substrate and feeding less (as apparently, some food gets to the bottom). The water change should help with negating the ammonia spike.

      Good luck!

  6. I used the terta safe start yesterday with a fish in the tank (im new) and my nitrites are threw the roof with no nitrates did I get a bad bottle?

  7. Hi! I started a fishless cycle but with plants. After reading your article I’m deciding to go with api QuickStart. However I have questions. Do I need use ammonium chloride first? And then add the QuickStart? Or what process do I take?

    Thanks! Will be adding pea puffers once my tank is cycled!

  8. How do you do this without a live fish

    • Hi,

      By adding fish food to the aquarium. It will start to decompose and ammonia will rise, kickstarting the Nitrogen cycle.


Leave a Comment

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