Platies uncontrollable birth?

I would not put them in that fountain pond they are not meant to have fish. Don't mix them either unless you have lots of hidins for the fry even then you will still lose some from being eaten, But you didn't want those anyway because they are the weaker slower ones. I've kept my platy fry with the parents as this is how nature does it with lots of plants for hiding. Sure out of 10 - 20 fry only about 3-8 will survive but they are the stronger faster fry that you want.