so a few weeks ago, my horrible biowheel filter completely died on my 10 gallon, to the point the motor stopped running. i went out and bought a new filter, a tetra whisper 10. i knew that there was going to be a minicycle and i tried to stay on top of it, but i lost 3 tetras and my betta that was in there now looks very sick (hes in his own bowl now, but just lays there). to top it off i had to leave town for a few, and i come back to two of the tetras looking very odd. they kind of seem to hide near the back, and their bodies are arched. the water was normal, nitrite-0 amm-0 nitrate-10, but i did a water change anyways. has anyone ever heard of this before? any help would be great