How do you tell?? (Might as well add to this) What about a female betta?? I may have a little problem. I like female bettas as you do, Joel, but yesterday the three that were available were very colorful - more so than usual and one of them had a lot more finnage. They weren't exactly small either so I didn't consider them juvies. Then I got to thinking. I have a dark red male (supposedly) that I have had for months. He has a very short round tail and it is not because of damage. I really don't want to test this out by putting a female in with him/her. On the other hand, if he was a she, I could maybe put her in the tank with the other females and get another male. I have noticed that some females, in spite of their color have a darker stripe on their side, but that isn't consistently true either.