Even for a well-cycled home aquarium, sometimes out of the blue you get a reading of ammonia or/and nitrite. When such incident has happened, we call it ammonia and nitrite spike, or a mini-cycle. We must fix the problem as quickly as possible to prevent fish from getting killed. To fix the problem, we must first determine the causes for the build-up of ammonia and nitrite.
Ammonia (NH3) and nitrite (NO2) are toxic to aquarium fish even with the lowest concentration. As fish keepers, we must keep both of them at zero in the aquariums all the time to keep fish alive. While most fish might not just drop dead on the first sign of low concentration of ammonia and nitrite, they will be permanently damaged if the problem is not getting fixed soon.
What are ammonia and nitrite? Why are they in the fish tank?
Ammonia is a waste released by the aquarium fish. Not only do the fish continuously produce ammonia through their gills, but the fish poop and leftover fish food will also break down and produce more ammonia. In other words, it is impossible to stop the continuous production of ammonia in a fish aquarium as long as there is fish. Nitrite is a temporary product of aquarium nitrogen cycle when some of the good bacteria in the aquarium system attempt to break down ammonia and turn it to nitrate. While nitrate is harmless at low concentration, nitrite is even more deadly than ammonia to the aquarium fish.
In a well-cycled aquarium, both the ammonia and nitrite readings should be 0ppm. If you have not done a fishless cycling before getting any fish, it is unavoidable to have a high concentration of ammonia and nitrite in your aquarium once you have put fish in it. Read for more information on fishless cycling if you have no idea what it is.
Possible causes for ammonia and nitrite spikes in a cycled aquarium
An ammonia and nitrite spike in a well-cycled aquarium can only mean one of the two things:
1. Bacteria colonies in your filter media have collapsed, or something has damaged it.
This can happen when you have used some strong medications for your fish. Or perhaps you have washed the filter media too “clean” by using untreated tap water or squeezed it too hard and too many times. When you have fewer bacteria doing their job of converting ammonia and nitrite to nitrate, it is easy to understand why there is a surplus of ammonia and nitrite in the fish tank.
2. There is an increase in ammonia production in the fish tank.
Either you have overstocked the aquarium with too many fish (More fish means more ammonia). Or something is rotting in the fish tank. It could be too much fish poop or leftover fish food, or even one or two dead fish.
How to deal with ammonia and nitrite spike in an aquarium?
1. Reduce the ammonia and nitrite concentration by doing partial water changes
A short-term immediate quick fix is to do partial water changes. A 50% water change will decrease the ammonia and nitrite concentration by half. Likewise, a 75% water change will lower them to only 25% of the original concentration. You may do partial water changes multiple times in a row to reduce the toxic to a minimal level. Make sure you never do a 100% water change or anything close to it to avoid shocking the fish.
2. Make ammonia and nitrite temporarily harmless
Some aquarium water conditioners can make the ammonia and nitrite less harmful or even entirely harmless for a certain period.
For example:
SeaChem Prime can temporarily detoxify ammonia by turning it to ammonium for up to 48 hours.
Kordon NovAqua+ can reduce the intake of nitrite for fish. If you use any of these water conditioners for every partial water change, you can minimize the damage of ammonia and nitrite to your fish.
3. Remove organic waste in the fish tank to reduce the ammonia production
All of these partial water changes are temporarily fix to lower the toxic, but not to eliminate its production. If you do not go for the source problem, the ammonia and nitrite will just build up again. That is why you must check your aquarium for any dead fish or other rotting organic matters. You may remove the dead fish by using a fishnet. The removal of all the fish poop, leftover fish food, and other organic debris at the bottom of the fish tank can be done by using an aquarium vacuum. You can do the vacuuming at the same time you do a partial water change.
4. Feed the fish less food to reduce ammonia production
Overfeeding fish is the #1 cause of water pollution in the fish aquariums. Under normal circumstances, you only need to feed the fish as little food as they can finish within 30 seconds. You must not see any leftover fish food after every feeding. In case of an ammonia and nitrite spike, you might want to reduce the amount of fish food your fish are getting whether or not you have been overfeeding. The less food you feed the fish, the less poop they will produce. You may do it by either cutting the portion of every meal, or feed the fish every other day instead of every day, or skip a few days of feeding in a row until the mini-cycle is over. Fish will be fine with no food at all for weeks.
5. Reduce the number of fish (or get a bigger fish tank and more efficient aquarium filter)
If too many fish cause the ammonia and nitrite spike in the aquarium, you must either reduce the quantity of fish in the fish tank, or you have to get a bigger fish tank with a more efficient aquarium filter if you want a long-term fix. You may also add a second filter to the existing fish tank to increase the biological filtration.
6. Fix the bacteria colonies in your filter media by having the aquarium fully cycled again
The good bacteria which feed on ammonia and nitrite prefer warmer water and more oxygen. They will multiply faster in a more comfortable environment. Just like when you do a fishless cycling, you can speed the process up by setting the aquarium heater higher to increase the water temperature to 86F+. You may also increase the water surface movement by adding more air stones to give the aquarium water more oxygen.
7. Use a live bacteria product to jump start/finish the aquarium nitrogen cycle
Fixing a mini-cycle in an aquarium with fish is the same as “fish-in cycling.” If you are willing to pay to fix the problem, the quickest way to restore the bacteria colonies in your filter media is to get a bottle of live bacteria product such as Tetra SafeStart. Get a bottle that is rated at least twice your fish tank size will fasten the cycling in the aquarium.
Sometimes a mini cycle might hit your aquarium unexpectedly. The above tips will help you solve the problem while minimizing the potential damage your fish might suffer from the toxic ammonia and nitrite. The same tips can also apply to those who skipped fishless cycling and later found the aquarium in the situation of ammonia and nitrite spike. If anyone has anything to add, please feel free to leave a comment.
A very informative and enlightening article for people who are in the dark about how to remove ammonia from aquariums
Thanks, Kevin.
Can we use tetra safestart during ammonia or nitrite spoke with fishes in the tank or we should take the fish out first.
Hi Umang,
You may use Tetra SafeStart while the fish are still in there. They will not be affected. It is (good) live bacteria after all. Dump the whole bottle in. Once it is unsealed, it does not last long.
Please help! My saltwater fish tank keeps spiking ammonia. It’s 55 gallon been running over a month. Using biofilter. Four bangghi Cardinals. Not sure it that’s spelled correctly. Two clowns, four damsils. Doing small feedings. Started with zero reading two days ago and has risen every day. Today it’s a 2.0. no dead fish yet. Please help. Added sea chem prime but not helping.
Also nitrites and nitrates are showing 0. pH 8. Salinity 1.023
Are you sure you have tested nitrate correctly? In a healthy fish tank, there is no way nitrate can be 0ppm unless you have only 1~2 tiny fish in a large fish tank full of live plants. What about ammonia?
Hi Karan,
How long have you been running this tank?
If it is new, have you cycled it before adding the fish?
If it is at least months old, and the ammonia spike had just appeared, you might want to think it through what has changed recently. Also, have you done any water change recently? The buildup of the organic waste at the bottom of the tank will contribute to ammonia spike eventually if they are not kept in check.
If you have been adding Prime, what you read is ammonium instead of ammonia, which is harmless for the fish.
We won a goldfish at a fair. I got a 2.5 gallon tank, a filter, a heater, and some gravel. The goldfish died that night. So the next day, we went to the store and got a betta fish. We got some betta food and a moss ball. I thought everything was good, but then I found out about the nitrogen cycle. I tested our water and the ammonia was at 4.0 ppm!! My tap water tests negative. The pH is 7.2.Our nitrates and nitrites were both at 0, I think because I had been doing daily partial water changes since the water was cloudy. I decided to get a larger tank. Now we have a new 5 gallon tank, with new treated water, new decorations, new filter, everything. I am about to put the fish in it. What can I do to make sure this doesn’t continue to happen? With the last tank, the only thing that I could identify as a possible problem was that my daughter may have been overfeeding the fish. Now we have pellets so the fish will only get 2 pellets per feeding. I have read that you should use previously used gravel if possible – but should I do that since our old tank was infested with ammonia?We only have one other live creature in the tank, a moss ball. Should I get other live plants?What should I do to be sure this nightmare doesn’t happen again? We are leaving for a few days and I can’t stay home to constantly labor over this fish tank. This is not at alll what I anticipated. I’m exhausted.
Hi Kristen,
It is the best to cycle the fish tank (or rather the filter) before adding the fish. However, since you have already bought the fish, what you may do is to transfer the water from the old tank to the new tank along with the fish (to avoid shock the fish due to sudden changes in the water temperature, etc.). You can also use either Prime as the water conditioner to temporary turn ammonia to the harmless ammonium, or get a bottle of Tetra SafeStart to jump start the cycle. At 4ppm, ammonia will kill the fish quickly. So doing partial water change will be an emergency temporary solution to lower it (but not eradicate it, because there will always be ammonia until the tank is cycled). You are welcomed to use our forum for further questions. It is much easier to go back and forth in a forum thread. 🙂
Thank you for this thread – I’ve been troubleshooting for a month and am still working through it. I have a 16 gallon freshwater tank and it had been cycled since February. A month ago, it got cloudy, then green, then ammonia started to show. On the recommendation of my pet store, I changed the filter (I have a BioCube and I think the filters need replacing more frequently than more substantial ones?) while worrying that it would affect my bacteria and I don’t know if it did or if I were already on that path based on the algae and then ammonia issue, but a week after changing the filter, I used a UV sterilizer to clear the algae and I’m worried that that also affected my bacteria. The UV is off, my ammonia was spiking and I had nitrite in the tank for the first time ever. Now ammonia seems to be coming down and nitrite spiking. I’ve been adding Tetra Safe Start daily and did a 50% water change last week and a 20% three days ago. Is there anything else I can do? If Prime is recommended, do I just dump it in the tank? Thank you for any help!
Hi Amanda,
You should not change the filter media. The beneficial bacteria for aquarium nitrogen cycle resides in the filter media. Once you change the filter or replace the filter media, you start all over again. During fishless cycling, you should do a partial water change once the nitrate is too high. You do not really need UV sterilizer for algae problem. Just starve them of light and nitrogen, they will be under control.
I have 11 koi fish in a 75 gallon tank. My fish are swimming to the top and I have to work in the morning. Can I put some prime in it while they are in it temporarily until I can fix it when I get home? I think I may be over feeding them and the old food is causing high ammonia levels. Please help! I don’t want them to die in the middle of the night!
Prime will temporarily turn ammonia to ammonium. It is a temporary fix. You need to do a partial water change as soon as possible with Prime. Remove as much debris from the gravel as you can when doing the water change. You might need to do several partial water changes several days in a row. Just make sure the water temperature is close to the tank water to avoid shocking the fish. Good luck! Don’t overfeed again. 🙂
I have read so many articles about this problem.
This is by far the clearest and smartest approach to dealing with ammonia spikes.
Partial water changes, siphon the gravel, add liquid bacteria and cut back on feeding.
Thank you for this explanation which will help so many with out getting complicated.
Great Guide, thank you
Thank you. Very useful and clear advice.
You are welcome.
If you have more questions, feel free to use the forum.
So far I am dealing with constant spikes in nitrite. I manage to keep it under control with water changes, live bacteria and gravel vacuums. Curious from those of you with more experience. Do bio rings help? I have an extra, although smaller, water filter that I have added to my tank with just the bio rings and filter fibers hoping to improve the level of good bacteria with less chance of disturbing it with filter changes or cleanings of the larger filter. Also thought of adding live plants, as of now I only have plastic. Any thoughts? 55 Gallon tank with about 20 fish.
Hi Bob,
I know this is a very late reply. If you still have a problem or if anyone else has a similar problem, I am willing to help. It is much easier for back-and-forth discussion if you can take the question to the forum. Here I will give you a quick answer. The rings used in the filters are to increase the surface areas for beneficial bacterias to colonize. So yes, they will help. In my favorite canisters filters, those rings are a part of the filter media. In a well cycled and maintained aquarium, you should not have constant nitrite spikes. It is either caused by unstable bacteria colonies, or the bioload is too much for your existing filters to handle. In the former case, you might have been constantly destroying the bacteria colonies during filter cleaning. I do not mess with my filter media when I clean the filter. Left them in a bucket of old tank water, get rid of the debris, and put them back, and that’s all. If the problem is caused by too much bioload, then you might want to cut back on feeding or reduce the number of fish. Or add extra filter media to your filter if there is still room. Not, plants will hardly help. Even if you cover the entire 55-gallon tank with live plants, it might only be enough to absorb the ammonia produced by two Neon Tetra size small fish. You are more than welcomed to use our forum. Provide a bit more details such as your filter models, and the species of your fish will be helpful.