Hi there, I just recently bought a male beta (sister wanted to buy the weakest looking one and try to save it), and also bought him a female. They got along ok for a little while, but the male always looked near death and rarely did anything. A few days later, the male died and we bought a new betta - lively and compatible with the female (made a nice big bubble nest, rarely flared at the female and they would actively swim around the bowl). Just recently however, my female betta (she's blue) started getting a brown colour. Also, the male betta started acting all sick (like the last one we had), and only got worse until he died today. From what I've read, chances are that there was some kind of ammonia or nitrate posioning... I'm just wondering, why are the males dying off, the female seems to be handling this well as opposed to the last two males (if the problem was that bad, wouldnt she have died as well?)
PS. I've cleaned the bowl and added some water cleaning agent before adding fresh water quite a few times. Also havent overfed them.