Looks like you have a few different types of algea growing on the rocks around the coral too. You don't want to look for a critter to clean the algae, you want to improve your water quality to prevent the algae from growing in the first place. Anything that eats the algae will only poop it back out and the nutrient cycle will continue.
You should be running a good, high quality protein skimmer, run a high quality carbon to remove dissolved orgaincs, run GFO
(granluar ferric oxide) to remove phosphates, do weekly 20% water changes to get your excessive nutrient problem under control and only use RO
water for water changes and top offs.