Why won’t the ammonia go away?


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Despite carrying out frequent water changes and cleaning, reader Deborah Smith is struggling to keep the ammonia levels down in her tank. Neale offers his advice…

Q) We've recently started our fishkeeping adventure with five Platies, five Zebra danios and five White Cloud Mountain minnows in a 57 l Fluval Flex temperate tank with artificial plants. We do a weekly 20% water change and gravel clean, and also clean filters as advised. We've added a second filter — a Fluval U2 underwater filter — as the included sponge filter didn't seem very efficient.

Our fish are quite happy, but we have constantly high ammonia readings despite regular doses of liquid ammonia remover, and the water is cloudy.

We feed Love Fish temperate flakes and have reduced feeding to once a day given the ammonia. Would switching to fresh food help the ammonia issues?


A) Neale says: Ammonia is constantly produced by the fish in the tank and any uneaten food, and the only way it is reliably removed is through biological filtration. Rapid plant growth can help to some extent as well. ‘Ammonia-removing’ chemicals most certainly will not. These exist to remove the fixed amount of ammonia in some tapwater supplies. Ammonia can also be present in tapwater when you add dechlorinator — when dechlorinator breaks down chloramine, widely used to sterilise water, the result is a combination of chlorine and ammonium ions. The dechlorinator obviously mops up the chlorine ions, but ammonia remover will be needed to lock away the ammonium ions.

In fact, most modern water conditioners contain both dechlorinator and ammonia remover for this reason. What ammonia remover does not do is remove the ammonia produced by your fish. Incidentally, sometimes you can get a ‘false positive’ result with an ammonia test kit after neutralising chloramine in the way just described. How do you get around this? Get some tap water, add some water conditioner, mix well, and do the test. If you still get the same non-zero ammonia result that you’re getting in the tank, a false positive is the problem. Case closed, and don’t worry about it. The filter will slowly process this neutralised ammonia and in the meantime, it won’t do any harm to your fish.

The odd thing here is that even if harmless ammonia is left over from conditioning your tap water, it should disappear within a day or two. If it’s staying there day after day, and showing no signs of going down, then that’s suspicious. If you find there’s no ammonia in your tapwater, so can rule out a false positive, then we need to think about another explanation: overstocking and/or inadequate filtration.

Your aquarium contains 57 l, which is only large enough for a few very small fish, so the built-in filter is likely lacking in terms of how much filter media it will hold. In the number you’re keeping, the Platies, danios and minnows are placing a fairly stiff workload on the filter. If you’re overfeeding as well, that’ll just make things worse. Small tanks are simply more difficult to maintain than medium sized tanks. I’d honestly recommend a beginner start off with something between 90 and 125 l.

A good quality dried food makes the best all-around staple food for small community fish species. Occasional offerings of live Daphnia can be useful from time to time because they reduce the risk of constipation, and Platies should have some algae-based foods in their diet, such as Spirulina flake.
A couple of meals per day is ample, and no more than can be eaten within a minute or two.

Also, remember that it can take 6-8 weeks for a filter to fully mature, and once matured, the media needs to be molly-coddled a bit. Don’t clean it under a tap, for example.