The Shrimp Of A Tank

My tank has tons of shrimp in it. When I clean my tank, I see shrimp swimming everywhere, but when I'm not cleaning, the shrimp are hiding. The most shrimp I've seen in my tank is sixty, but we have moved some shrimp into my mom's tank, so now forty is probably more accurate...more shrimp have been born, though, so maybe they have gone back to fifty.