I have 2 mollies and a plattie. My white molly has gotten quite fat. Can they gain weight if over fed or do you think it's pregnant? I didn't ask at the pet store if I was buying males or females and the 2 mollies were out of different tanks. The black and white one has stayed the same size and so has the plattie but my white mollie is really big around the tummy and front of the body.

Normally a fish just gets larger and larger as long as it lives. An unbalanced diet could cause it to put on more weight, but goldfish the males tend to look long and lean, the females look short and round. She probably is carrying eggs. They normally lay the eggs on rocks or plants like chickens lay eggs, then the male fish fertilizes them there. They don't give birth to live young the way guppies do.

i have 2 mollies and a plattie. my white molly has gotten quite fat. can they gain weight if over fed or do you think it's pregnant? i didnt ask at the pet store if i was buying males or females and the 2 mollies were out of different tanks. the black and white one has stayed the same size and so has the plattie but my white mollie is realy big around the tummy and front of the body.

Your fish is more than likely pregnant. Mollies are livebearers and DO give live birth to their babies and are always pregnant when bought from a store
Because they are usually mixed with males at some point in their life.
They have the ability to store sperm also and can still have babies if no longer being kept with males.
You can tell the difference between all live bearing fish by the shape of their anal fin (the fin on the under side of their belly).
A female will have a triangular anal fin.
Picture of a female molly, you can see the shape of the fin.13047


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The males have a gonopodium which stays tucked in on the under side of the belly unless they're trying to mate.
In that case they will follow the female fish around pointing it at her so to speak.
Picture of a male molly with a gonopodium13049

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Livebearers will eat their babies, so having a lot of good hiding places or a birthing container and a baby net will help with their survival.

Wow that's adifferent fish from what we always called mollie, the goldfish with the protruding eyes. Sorry!