Best thing i found for fry was lots and lots of plants and rocks for them to hide in. I have sucessfully reared fry in tanks with other fish jsut by providing enough hiding spaces. Java moss in brilliant for hiding fry if you can get hold of some.
Breeding is easy, get 1 male and 2-3 females and you will soon have plenty of fry.
Your going to be waiting a good while for those goldfish to die. If you dont want them might i suggest you rehome them to a pond or someone with a larger tank, since i can proberbly guarantee the tank they are in at the moment is not big enough.
Good luck.
Laura
I have just read your other thread and am glad to hear your rehoming those goldfish