safer way is to use something like kent liquid calcium and a syringe/needle and inject them. WIll kill them and not nuke the tank. I read it on an other forum for getting rid of aptasias. Works pretty well. I get a syring from the local feed store for giving dogs their shots, draw some of the liquid calcium into it and stick it into the aptasia and squirt osme into it. Never see the little bugger again and the ph never rises like kalk paste causes it to do.