You are dead on with your diagnosis!! The green in the Majano are a dead give away. Peppermint shimp and or a mated pair of file fish will do the trick. You can also just remove the rock very slowly as not to disturb it then let it set out for a few days in the sun. I would sure hate to see you do that because blue sponge is awesome!!!! The Majano should be removed as they are hard to kill.