Amonia in aquarium

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Registered Member
Original poster
Nov 16, 2018
I have been loosing a number of fish. All rainbow fish. Went to my pet shop and found i have ammonia in my tank. I have been doing water changes every day with no success. Other fish like my congo and black tetras, gouramis,angelfish and catfish are doing ok. So my question is why only my rainbow fish are dying? I am about ready to tear down my aquarium and start over. I bought my 29 gallon tank used. Is it possible it was previously contaminated? I have had aquariums since i was a little kid so this problem i have is very frustrating. Anyone with any thoughts ? Thanks.


Global Moderator
Staff member
Jan 11, 2013
West Falls NY
Real Name
Welcome! Do you have a water parameter test kit that allows you to measure for ammonia, nitrite and nitrate in parts per million? Even test strips would be a help at this point. It sounds like your 29g does not have a nitrogen cycle happening to support the stock you have.

If you could get ahold of a sock of gravel out of a healthy, established tank or use a sponge bubbler filter, or other filtration media out of a tank that's been setup for a long time, this would speed a nitrogen cycle along for you.

Other than that, it sounds like you have too many fish in that 29g. You're on the right track by doing daily water changes, but you need to keep doing water changes until you measure no ammonia (if fish are in the tank). I wouldn't hesitate to change the water right down to 80-90%.

Another thing that would help you is a quality dechlorinator that also detoxifies ammonia and nitrite. Seachem Prime or the granular form Safe are two really good products for that.

In the meantime, if you could re-home some of your fish, that would help. Other than that, lots of big water changes with using Prime as your dechlor.
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Aug 4, 2011
Phoenix, AZ
Judging by the "went to my pet shop and found I have ammonia" comment, it sounds like you don't have your own test kit. API master test kits are pretty reasonable at about ~21 or so, and pretty reliable. The kit will last a year or so (make sure to make note of expiration dates). It's a good tool to begin diagnosing issues.

I was thinking you had a lot of fish for you tank, considering schooling sizes for some of those species you listed, and then I saw you say it was a 29, and I think you're in for a lot of work. That sounds like *much* too small of a tank for those fish. Huge daily water changes are in your future if you don't want to lose more or rehome some.
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