Guppies!! Depending on what you are feeding set-up a 5-40 gallon breeder tank bare with no substrate, a sponge filter so fry dont get sucked up, and a massive chunk of java moss.
I started with 6 guppies in my breeder tank and now have over 100 6 months later. I just leave the java moss in the tank and scoop em out as my frogs need em. I feed them cheap wardleys flake, and dont give them any special attention. I dont keep a heater in the tank, it has a small power filter (not a good choice I lose fry and males occasionally if they are small enough to get sucked in the grate.) but I got sick of the sponge filter and I rarely lose fry to the filter. In fact most of them like the current once theyre a couple weeks old.
Ive also dealt with ghost shrimp, maybe I was doing something wrong, but I had a hell of a time keeping the fry alive
