Im not sure, maybe something small like neon tetras?
Something else you might want to try. I used to keep F8's and I also bred ghost shrimp to feed them. It was fun. But I also bred those typical pond/pest snails in there with the shrimp. You know how sometimes if you buy plants from some lfs
and they already have some pond snails on them? Well Walmart told me that, of course, lfs
have problems with that too. The snails end up in their filtration system, so they just opened up the filter and scooped out a handful and gave them to me for free! Of course there was no trouble breeding the snails either! Had tons of them.
55 gal with 3 fancy goldfish. 2 goldies in QT, 23 flatback hex tank with betta, 3 ADF's, 2 BN's and nerite snails, 60 gal community tank: 4 angels, rainbow shark, raphael cat, apple snails,etc.