Just got back from vacation and came back to a bloom in hair algae. We have taken it out manually but I want to get emerald crab to make sure it stays down. I have a 90 gallon mixed reef tank with only 4 small fish in it (2 clown, 1 goby and 1 6 line wrasse). How many emerald crabs should I have and what is the maximum that i should have? I know in order to keep my reef safe we have to make sure they are well fed.