You shouldn't need to feed them anything in particular. If you are only feeding algae, I might drop some pellets in for them every once in a while. Otherwise, they should eat whatever you are feeding your fish...
They will eat aiptasia and other small anemones and any meat bases pellet or flake.had mine in frag tank and he took care of 3 aiptasia that showed up on colony rocks so I kept him fed well and one morning caught him cleaning a montipora digitata frag and thought cool must be something bad on it and came back an hour later and it was stripped to the bone with just a few purple specks left on skeleton and he got put in display with no issues so far in a few months.the digitata was a neon green montipora and has grown back to where it was before eaten and strange think is it is a deep maroon and purple color now so he may have made a new designer montipora digitata.the wife and I have called the new growth peppermint wipeout