So you have male guppies in with female platys? Do they try to breed? Those offspring will be sterile, right? Do you have male platys in there too? Do the male guppies fight with eachother? I can handle one brood of sterile guppy/platy offspring I guess.
I was going to get an all male guppy tank but many many people advised against it saying the guppies would get all aggressive with eachother.