Mine's eaten all of mine. It took it a couple of days to decide to roam the tank but once it did, it made short work of it all. There was one large one that it took its time with (took several days for it to disappear, but it got noticably smaller every day). There's another little one that I found when I moved my rocks around the other day, but I'm sure it won't last for long.
"They" say that there's a 50/50 chance that you'll get a peppermint who's interested in eating aptasia. Hopefully you got one that finds the stuff a delicasy.