I bought a couple of peppermints a little while back... they were so young, you couldn't even see the strips on them. For awhile, I thought they died in my tank until I cleaned my sump... and there they were, about twice as big
.
They don't touch anything in my tank and only come out when food is present in the water column. Every now and then I would see one of them carrying eggs, which I assume turns into good quality food when the larvae get released into the water.
-Rich