Or do I just need a new tank?
I posted in another thread about how my daughter's fish died after 5 days. He looked absolutely fine - swam a lot and was alert, and then in the morning was dead.
I have a thermometer in the tank (no fish now - just water and ornaments) to see if it stays warm enough over a week's period. Temperature is the only potential problem I can think of, other than just maybe having a sick fish.
The pet store said we wouldn't need a heater, and I really can't find a reliable heater for that size tank right now. I've been reading reviews and all the smaller heaters seem to cause problems eventually.
So I'm wondering if I just need a larger tank in order to keep the fish happy?
I'm a little confused!