At this point, there are 3 I've used previously that I won't anymore for different reasons.
Urchins: these suckers will brazenly break off any coral not encrusted to the rocks or secured with an ugly amount of adhesive. Worse yet, if it's a pincushion, they will carry this coral to the part of the tank that you cannot reach and deposit it there.
Emerald Crabs: why, youay ask? Well, my friends I have I believe 5 in my display right now and 7 in the fuge. The reason? Those 7 have all been spotted raking flesh off of healthy corals. Honestly, not worth the risk imo. My rabbitfish does a better job eating any bubble algae, anyways.
Peppermint shrimp: these guys only have about a 30% success rate of eating aiptasia IME and far more frequently will tear apart any fleshy LPS to get to the food that they catch. Again, not worth the risk.