My tank's helpful fishes:
Lawnmower blenny - Cleans the every day algae
Melenarus Wrasse - Takes care of any pests
Tangs (yellow, blue, sailfin, scopas) - Eats any algae that they can find
Mandarin Goby - I assume he would eat any flatworms that he can find, but I have never seen any so its speculation
The other 10 or so are for coral food