Alright, before I ask about tank mates, what kinds/brands of heaters work best? I am on my third one in a week, and of course it's not working...grrrrr . Anyway, once I can find one that works, I'm going to get three female Bettas for my 10-gallon tank. I've been wondering what other kinds of fish I could have with them, and I thought cory cats sounded good. I've heard that some fish need more aeration than Bettas do, so will cory cats be okay with just a filter and heater, or will they need some special equipment to put more oxygen into the water? Is a pH of 7.2 and temp. of 80 F okay for cory cats? And will three Bettas and 4-6 cory cats be too crowded?