Freshwater Fish Tank Diseases Symptoms

HELP!! My fish keep dying!!!!?

I have started a 29 gallon freshwater fish tank about three weeks ago. i have everything a Bio-wheel filter, air stones, heater..water temp always between 78-80. I have about 15 fish in there now…they are small a few danios, few tetras, few guppies, 2 red tail sharks, 2 albino sharks 1 algae eater…not sure the name and a few others. I brought them all from a local pet store. I have not yet done water cleaning, i do regularly check the water with test strips for all things, ph, ammonia, nitrate, and so on. All the tests have come back normal. The person at the pet store instructed me to feed the fish ever other day. The algae eater died first and the one of the danios i look at the fish and i did not see and spots or signs of disease…the were symptoms b4 they died… Can someone please enlighten me on what i am doing wrong!

First was your tank cycled prior to adding any fish?

http://freshaquarium.about.com/cs/biologicalcycle/a/nitrogencycle.htm

This site will help you understand the nitrogen cycle process.

Secondly a 29 gallon tank only 3 weeks old shouldn’t have over 15 fish in it already. Fish should be added slowly only a few at a time about a week apart. your biofilter needs to readjust to the added waste inbetween additions.

At the time you “tested” your water, your ammonia or nitrates may not have been spikeing. More than likely it has spiked with the addition of new fish or so many at one time. Fish need fed everyday not every other day. You need to clean and water change 25% on a weekly basis. This keeps the nitrites and the ammonia in check as well as the nitrates

Also when you get your new fish, you need to float them properly and allow them to adjust to your tank.

Tetras Negros (Gymnocorymbus ternetzi)