This would also depend on what other clean up crew you have. You dont want them to go hungry, but if you really like them alot you could safely have 3 to 4 in a ten gallon with out too much problem. Personally, if you like shrimp, I think you should check out sexy shrimp. You can have a whole herd of them in a 10 gallon, and they have great color and personality. They cost less then peppermint shrimp, and are so much fun to watch. Good luck, hope that helps.