Well, what I do in the case of livebearers is just let the females drop the fry in the community tank once I get to the point of not knowing what to do with them. Unsavory as it is, the fry will be a very good source of healthy, parasite free live food for your other tank inhabitants. Sometimes, though even that does not control the population.
The
LFS may take them off your hands to be used as feeders, but they will likely not give you trade-in on them because so many people are in the same boat.
You can also just trade back the females and stick with males. If you have more males than females these girls are going to stay gravid all of the time and it will literally wear them out.
__________________