I know tha most peeps would say to have no stones and a sponge filter but I have sooo many fry at any given time that I keep a 29 gallon tank set up with gravel and 2 HOB filters.... it has perminant occupants 3 species of corries, and applesnails, and the fry come and go as I have them. at any given time there are anywhere from 50 to 150 fry in various stages of life swimming around happily. I like to keep my temp set at 78 degrees.
my fry tank is just another aquarium with mini fish in it. once they reach a size where they start to go after the newborns I take out what I want to keep and take the rest to my friends lps for store credit. that helps on the supplies and she gets to sell my fry to others What works for me may not work for others.... it's all a matter of what works for you. Good luck on your fry!
I use those little whisper 5-15 filters.... I have 2 of them for my 29 fry tank. if you use a HOB filter like I do it's recommended that you put pantyhose over the intake so the fry don't get sucked up into the filter. I think that with a sponge filter you don't have to worry about that but I am not sure as I have never used a sponge filter hope this helps