Black Mollies telling what sex

[Lex811117]

I have two tanks of black mollies that i have had for about 6 mths. They breed like crazy and I want to stop this. I have a two part question.

The first, how do you tell which is male and which is female? I know the male has a modified anal fin, but i am not sure what this means. If someone could show me pics of examples that would be great. I was thinking of putting all my male fish in one tank and the female in the other.

This leads to the second part of my question. Is this a bad idea (granted that i properly move them)? I dont want to do something unintentally to hurt my fish when i am just trying to help them from over crowding.

Thanks

[kveeti]

There's a good thread showing pics of the difference in male and female livebearers here:
http://www.aquariacentral.com/forums/showthread.php?t=33109
It's of guppies but the fin part is the same idea.

[pwrflpills]

It's pretty easy with Mollies - the females have a fan like anal fin. You know, it looks like a fin.

The males have more of a, excuse my french, "rod" or stick like anal fin, that doesn't really look like a fin, but more like a little bone or something.

As far as separating them, I have 3 female black mollies and that's it. They seem fine. I think it would probably effect the males more and they may tend to fight or something if overcrowded and with no females to distract them.