ever see something like this?

 

Too many hermits in a the tank cause problems because they get too hungry and then get aggressive looking for anything to eat. When they get this way, half of them should be traded for snails.

 

One of the biggest disasters for a reef aquarium is not having enough snails to prevent an algae bloom. Snails eat the hair algae when it is just a sprout on the rock that we cannot even see. Without sufficient snails, the sprouts grow and as they grow longer these older, tougher algae fronds become distastful. This then allows the hair algae to multiply and spread to other areas of the tank. To be sure, too many snails can create starvation but I'd rather see too many than not enough. A few extra hungry snails can be removed and placed in another tank in need, but hair algae once started, requires considerable time and patience to remove.

 ...Yet, a green haired mermaid can be interesting  http://www.garf.org/ugly.html