I dont seem to have that problem with my bigger fish, but i have set and watched my snails do that, i had a 14 inch black and white urchin that was really bad for tearing my stuff up, and a pink rose urchin that did the same thing, kinda sucks, but then thats what this hobby is all about right, haveing your tank mimic what the ocean is like, so thats what ive been doing letin nature take its coarse, and hope it dont look to bad lol