Two of my female bettas were in a 20 gallon I had running, waiting for some red top kimpunas I got off a buddy. They're tank was getting an overhaul. I put my white male in there while I was get his tank rescaped, figuring they would dart away and hide but everyone would be okay for a little while. No, they went freaking wolf pack on him after I turned my back. Got him out, put him a two quart jar to chill out. He looked okay. A few fin tears, but otherwise, more just a little shaken up than anything. Then next day, I got my red tops and went to net out the female bettas and move them to their new home only to find each one dead in a separate corner. After reaching my hand in to pull them out because the net was getting caught on decorations, I realized the water was freezing. Some how the heater had come unplugged(I have a nearly two year old and a dog) and coincidently the furnace was acting up the night before causing the house to get pretty chilly. That sucked. I had both of them almost since I started keeping bettas. The next day, my white one up and died with no real warning since he acted fine since his incident. That hurt, my mom got him for me because I fell in love with how pretty he was but had sworn not to buy any fish for a while, so she got him for me so could get around that. Then today, I go to feed the guys I have left, and notice my brick colored veiltail isn't popping out of his hiding places to snap up some food, I pull the stand out and look at the back and there he is, dead, wedged under the heater. I'm going to guess he swam under there during the night, got stuck, and suffocated. This has been the most frustrating week of fish keeping I've had since I started out and did everything wrong before doing some research and learning the right way to do things.