water too cold

I had a betta in a 5 gallon, with heater and filter. The other day I realized she was acting really lethargic. I realized her heater wasn't working like it was supposed to. So, since this was an emergency situation, I took the heater from my other tank to place it in her tank, so she didn't...

These poor Zebra danio's (only 2 left now) have been to hell and back. About a week ago one of my danios was being severely bullied by another one - and was literally starving to death (no idea why the stupid fish didn't eat the extra's that fell to the bottom floor like all my other species...