Well,a couple of suggestions.If you are setting up the tank strictly for breeding purposes,I would go with plastic plants.The reason being that when you go about the inevitable collecting and thinning out of the Platy fry,you wont have to worry about damaging the plants.Fry are good at escaping your probing net and can give a good chase.Also,you wont have to worry about caring for the plants,i.e. light and pruning.My favorite to use is plastic green cabomba.But,any fine leaved reproduction will do.However,if you do use live,I like Water Sprite(Ceratopteris thalictroides) and Hornwort(Ceratophylum demersum).But,everyone has their faves.Good luck...