Those things are a real pain to get rid of. I had so many of them in my 200 gallon that I just took the whole tank down, dried out all the rock and started over. I had a purple lobster that would kill all the peps I put in the tank, and I could not keep the copperbands alive. When I took the tank down, I got rid of the lobster and I now have no problems keeping peppermints.