I use to have a seahorse & pipe fish tank that I fed mollies & guppies to. I had a couple males and several females in a 30 breeder that were acclimated to salt water. I used a couple sponge filters run with an air pump, no gravel and some pvc pieces for hiding places. The nice thing was that if the fry didn't get eaten right away, they would live indefinitely in the seahorse tank until some one got 'em. The mollies sometimes would get too big for the sea horse but the guppies were so small that they got eaten pretty quick. I sometimes used a turkey baster to remove the fry from the tank to transfer them to the seahorse tank. The mollies were great algae eaters too, often wondered how they would do as an algae eater in a reef tank or something. As per feeding them to your panther grouper, the fry would be so small that it might not be interested in them, you may have to grow them out.