sick tetra

Question
Hi I have 4 tetra's in a small 2 gallon tank, and one of them started to float vertical near the top of the tank.  I thought he was dead but when I tapped on the glass he moved.  It's been about 15 hours.  

tank set up 1 months ago, 2 gallon, all 4 fish are tetra, small $5 filter (not sure of the name, but it has rocks/charcoal on one side and a white sponge on the other that turns black as it works) I have to change the water and filter 1 x a week or the water gets to dark and stinky.  I use tap water with a conditioner.

Thanks!

Answer
Hi Dawn;

It's hard to say for sure what is wrong the one fish but it doesn't sound good. Try changing part of the water and see if that helps. I do see a serious problem with your setup though and it may be why one is now sick. Hopefully the others don't follow. Your tank is going through something called the "break-in period" and too many fish were added to get that started safely. That's why the water smells. It isn't balancing biologically yet and waste toxins are building up. Every time you clean the tank and the filter all out, the break-in starts all over again. Here is a link to my page about it to help you know more about it and what you can do to help your fish get through it better;

http://www.xanga.com/Expert_Fish_Help

Tetras also need more room to swim and get exercise. A 2 gallon is far too small for even one. They are a very active fish that like to be in large groups, frolicking together in plants and other decorations. I don't recommend smaller types of tetras be kept in anything smaller than a 10 gallon, 20 or larger for bigger varieties. Tetras are also tropical fish. Unless your house is kept at 76f to 78f all day and night, even in winter, they are going to have trouble. Temperature fluctuations are very stressful to them and they will get sick eventually. Get a 10 gallon or larger with a good filter and a heater and they will love you for it! Read my article before you get a new one started though. It has important information you will need.

At Your Service;
Chris Robbins