How can you tell if your balloon molly is a girl or not?

Answer 1

If it is housed with males it is pregnant, 100%. Female livebearers pretty much spend their entire lives pregnant when they're kept with males. Males do not hang around! Females can also hold on to sperm for around 6 months and up to around 3 spawns when their are no males present, which is why female livebearers are so prolific!

The problem with deformed Balloon Mollies is their stunted shape means giving birth is complicated and you often find Balloon Mollies die from birth-related complications. The "balloon" shape is a genetic mistake been bred into Mollies by unscrupulous breeders, normally these fish would have been culled in favour of healthier regular shaped Mollies!

Answer 2

Look at the rear fin that is underneath the belly, the farthest fin back, right before the tail fin. In a male it will go straight back and in a female it is rounded down. If the female is pregnant you will see a dark spot in the rear of her belly and if not preggie then it will be clear to look at. They are live bearers, meaning they give birth to live baby fish or fry. You should have lots of plants in your aquarium to protect the babies from being eaten.

Answer 3

If your balloon belly molly is a female the anal fin will be rounded. If it is a male the fin will be more of a point.