Looking at the shape of this female, it's a Humpbacked limia (Limia nigrofaciata). The tiger limia (Limia islai) is a bit different in shape but has the same pattern on the body. I wouldn't know why they couldn't be kept with your present stock. They're easy to maintain. They're friendly. They won't chase their fry. If you can keep platies in there without a problem than humpbacked limias won't be a problem either. But they can crossbreed with mollies, endlers, guppies and Micropoecilia species. But that hardly happens when you keep both genders of those species in there. Then they'll choose one of their own to mate with. They can be kept at room temperature without a problem.
