Is it common to have a tank of platys breed out of control? I have 4 tanks with platys now. The only time any fry survived was when I put the mother in an empty 10 gallon, and took her out after she had the fry. No fry have ever survived long enough for me to even notice them in my other tanks. I assume they are eaten by the parents and other fish in the tank. Also, i don't have any of the dense, fine leaved plants that fry seem to have more success hiding in.
I was about to recomment platys to a friend who is starting fishkeeping - but I don't want them to have a population explosion!