And therein lies the aptasia control problem, at least for us. I've purchased larger quantities of peppermints and intentionally starved them in a holding tank where all they had to eat was aptasia. They ate it well and cleaned it up. We have since moved several of them to 3 other tanks and in no other case now do they seem to be willing to eat it any longer. The food available for them in the tanks seem to be preferable to the aptasia. I believe that if the tank is feed well, it's not real likely they will venture very far (if any) at all to eat aptasia even if they've been trained to eat it. On the other hand, it's possible that they may be taking care of the very tiniest ones and allowing any they don't see to get too large for them to want to eat.
We have also been using them to 'pickover' any zoo colonies that we've added recently in the hope that they *might* disturb/eat any of the zoo spiders and/or other zoo predators. They really go over the polyps *much* better than I can and for a few days they really seem to scour them well. I can't prove yet that they are eating/helping to control any zoo pests, but it sure appears like it.
I like them in general and they will sometimes spawn and produce lots of little foods for the rest of the tank too.
Doug