Toothbrush method... i use them sometimes for my star polyps. when the polyps sense movement, a predator or food in thier "mouths", they close up. for my star polyps, sand and algae would cover them and they would begin to close and stay closed, thinking it was food or a predator. what i did was use a very SOFT brush to lightly brush the tips of the polyps, ive used a siphon to siphon the dirt away too. this clears up the polyps and they open again. however my zoos have also dont the same thing as yours. ive had them for years and one day they just all closed and a few died off, i looked on SWF and noticed it happened to many people. they are slowly opening up and growing back, although some look bleached. i have no idea what caused it.