You can do shrimps no problem. There are something like 5 or 6 species that are commonly labeled for feeders as "Ghost Shrimp," so get some Cherrys, or Amano Shrimp. I have Cherrys in my convict fry tank, and everything goes great. If you see a shrimp eating the fry - I can ASSURE you, the fry died before it was being eaten. Cherry shrimp are NOT predatory, and will not kill anything other than brine shrimp, and of course algae. Some species labeled as Ghost Shrimp I've heard of killing fry, but Cherrys have a prestine record, as far as I know.