I know this is kind of a funny question, but I bought half a dozen red platies from my LFS about three months ago. One of them was hugely fat, and I assumed she must be pregnant. A couple of weeks later half a dozen little red fry appeared in my tank, so that seemed to confirm the theory. Thing is, the fat one continues to be just as fat as ever, but there haven't been any more fry in the couple of months since. (All of the original 6 fry survived, so I doubt there were a lot more that have been eaten.) So now I'm wondering what's going on. Is it possible this one fat one is actually a balloon molly? As far as I can tell, she looks exactly like the other platys - same exact shade of red and everything - except that she is noticeably bigger than the rest. I'm wondering if somehow she's a balloon molly that accidentally got thrown in with a bunch of platies, and if my 6 fry aren't actually from that fish. Is there a sure-fire way to tell the difference between a molly and a platy?