i dont think criters n stuff like that apply towards 1=5gal, being that they dont take up swimimng room they usually on the sand bed or the rock works. but some shrimp sometime dont like other shrimp,i read that pistol dont get along with coral banded shrimp. in that saying its not about how many shrimp u can have but what kind of shrimp will get along. cant help u much on the shrimp department being that i only have i peppermint shrimp, a good old coral banded shrimp and a cleaner shrimp. they get along fine but sometime coral banded shrimp get a little aggresive

but nothing serious.