I am trying to breed my mollys as I have a 300L tank which I only want to have fish I have bred in it. I am new to All this and I am not sure if this molly is pregnant or not? Thanks for any help!
She looks well shaped. She could be pregnant or just well fed. Also with this one, a clear gravid spot is not present. Which is quite normal for most female mollies. They've got too many color cells at the spot where the gravid spot should be.
To answer your question... Maybe?
Mollys, like the other popular Livebearers, can store sperm for the future. So if she's one of the ones you just bought, she probably is.
Also, I wouldn't worry about separating the babies. Since these guys give birth every 6-8 weeks, your tank would be overrun after six full batches. Just throw in some plants, leaf glitter and rock work for hiding places and let nature figure it out.