All Of My Fish Are Dying!

I set up my 20 gallon tall tank about a month and a half ago, using top fin quickstart and top fin water conditioner to get the party started. I waited two days, then tested the water before going and picking out 5 guppies, three cory catfish, and two snails. A few days later, I went back and got five neon tetras. The neon tetras were getting caught in the filter and all of them eventually died, so I thought maybe I just got some weak fish and those were too small for my aquarium. I decided to get five serpae tetras instead. After adding this second batch of tetras, I noticed one catfish missing. I didn't really pay any mind since they like to hide. But another week or so later, I realized there was only one catfish visibly swimming around and after doing water changes, I couldn't find the other two. I've been testing the water intermittedly using the API test strips and there never seemed to be a problem. I use the site aqadvisor.com to make sure I'm not overstocked and to see the overall parameters for my fish. As more time went by, I noticed my serpae tetras disappearing as well. Now I have four guppies, one tetra, and my snail. I also have a bubbler in my tank that creates a large layer of bubbles over the top of the water, and I read that this could be from excess protein in the water. They are clear bubbles that don't smell, they just don't pop as they should. Although the bubbler was a later addition to the tank, I am wondering if maybe it gives some indication to what is wrong. After testing the water just now, the readings are PH: 6.3 Nitrate: 0 Nitrite: 1 KH: 90 GH: 60. I know that my PH is a little low and the Nitrites are a little high, but I have been wary of adding any of the Top fin stuff because I've heard it can do more harm than good. I don't want to keep killing my fish, and they all seem very happy in their environment, but I don't know what to do and I don't know what it actually killing them. Please help!

It sounds like you didn't actually cycle your tank. Truly cycling it involves dosing with ammonia over several weeks until enough beneficial bacteria develops to handle a load of fish. There are helpful threads on this forum about cycling a tank. Pet store employees often say you just have to set up the tank and add a few chemicals and then let it sit and you can add fish. That's not true and leads to issues like this.

Do large water changes every day (75%) to get ammonia and nitrites under control. I would recommend adding plants as they will take up nutrients (ammonia) out of the water so that it doesn't harm the fish while your beneficial bacteria develops. If you get enough plants, they will keep the water safe for your fish. You ideally want fast growing plants, like Elodea Anacharis, Hornwort, Water Sprite, Water Lettuce, Duckweed, etc. Slower growing plants, like Java Fern, Anubias, etc, will help but not as much.

If you can't find those plants at the store, they can be purchased online.

I agree with @squidneh do a 75% water change right away that may help with the problem and it does not hurt to flush the system, Make sure you treat the water with conditioner and try to have it near the same temp as the tank water. Can you post a picture of the tank please.

Sounds like what happened me. Sticking with 75% daily water changes while ammonia and/or nitrites were above 0, it nitrates above 20, was so worth it. Really helped adding floating fast growing Salvinia, and also amazing sword, elodea & moss.

Best of luck with getting the cycle under control. This a great place for help, advice and support.

squidneh said:

It sounds like you didn't actually cycle your tank. Truly cycling it involves dosing with ammonia over several weeks until enough beneficial bacteria develops to handle a load of fish. There are helpful threads on this forum about cycling a tank. Pet store employees often say you just have to set up the tank and add a few chemicals and then let it sit and you can add fish. That's not true and leads to issues like this.

Do large water changes every day (75%) to get ammonia and nitrites under control. I would recommend adding plants as they will take up nutrients (ammonia) out of the water so that it doesn't harm the fish while your beneficial bacteria develops. If you get enough plants, they will keep the water safe for your fish. You ideally want fast growing plants, like Elodea Anacharis, Hornwort, Water Sprite, Water Lettuce, Duckweed, etc. Slower growing plants, like Java Fern, Anubias, etc, will help but not as much.

If you can't find those plants at the store, they can be purchased online.

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Oh, okay, thank you! I do have four plants, but I'm blanking on the names at the moment. I'll start the water changes and look into those plants you listed. Thank you so much for your help!!