I had one, a rather large one in my 20h.
He just hid in the back of my rocks sticking his legs out to search for food, though at night he did come out and climb around some things occasionally.
I had a reef tank, it was mainly Lps, but lots of inverts, and I never had a problem with him.
In fact my tiny Orchid Dottyback did the most damage, tore up my clown, killed a blood shrimp...