Maybe A Pet Store Oops?

[Arrowslinger]

I got this black lyretail molly

She is in a tank that contains four male swordtail/platy crosses, I swear she looks pregnant just in the last few days?

Could it be a platy instead?

 

[helterskelter]

Yes she pregnant.

These fish can store sperm for upto 6 months, so they can get pregnant with no males around.