I just added a few new items to my 215 gallon than that has been set up for approximately 4 years. I have not lost any live stock until I added two cleaner clams a few days ago. The first one disappeared (gone with no remains) the first night after they were added and the second one was gone on the second night. I have all reef safe livestock. Shrimp (peppermint and coral banded), 2 brittle stars, approximately 10 crabs (emerald, sally lightfoot and scarlet leg hermits), about 60 snails and various fish. Oh and one 12 inch lone bristlr worm. Nothing seems strong enough to relocate a clam. Any ideas?