Ok boys and girls this is a pic of my new emerald crab that I bought to take care of a small bubble algae problem well he seems to have taken a liken to my coraline algae normal behavior or does he need glasses
like mudplex said he is just scraping off micro pcs of algae and other junk So he is cleaning it when he finds the bubble algae maby he will gobble that up for you but it is not a given some do some don't
good luck
Manny