My Pencil urchin eats all the mushrooms. Couldn't figure out what was causing them to disappear or be half gone in the morning, until my wife found him actively consuming a green frilly mushroom one day. After he was moved to the sump the wounded mushrooms have recovered, and we've lost no newly added shrooms. I have a variety of Rhodactis, Discosoma, and Ricordeas that are all thriving with him gone now. Even the mushrooms I thought were completely gone (the pink with green spot Discosoma in the top right of the pic) seem to be recovering from the tiny bit of flesh left behind. Back up to 2 polyps now. I did have to replace my red with blue spots Discosoma though, they didn't come back