Bettas at lower temperatures are more prone to illness. They CAN be kept at 70 degrees quite easily. Many live this way for years, and never get sick. It just makes them more susceptible to any crap that comes their way if their water doesn't get changed, or if they get stressed, etc.
Bettas don't mind being alone so much. They aren't like other fish, that require companions of their own species. But they do enjoy the presence of their own species, to some degree. They just can't be allowed to reach the other fish of their own species, or of species that look remotely like them. And, while there are some males that will live peaceably with a female, there are so many that won't, that it is simply not worth the dead female...or the dead male. Because sometimes the girls are just as vicious, or they are forced to fight back against an aggressive male. Either way, it CAN and frequently DOES get ugly. I won't even leave a breeding female in the spawning tank with the male unless I know both of the fish in question, have watched them A LOT interacting together, and can check back with them at frequent intervals. Because disasters happen. I had a male and female that I turned my back on for less than an hour, and they tore each other up pretty bad. They both lived, but it's not for lack of trying to commit murder on either of their parts.
They are, however, wonderful pets. And, with the use of a divider, and you can one male, one female, in the same tank, able to look and interact...but not touch.
