I have had mine for about 4 months now and he occasionally helps himself to a midnight snack on a snail but for the most part he has left all coral alone. I would not trust him with any clam, asking for trouble. Could be fine then one day, bam, gone. Mine is in a 90g corner tank and seems to pace the glass a lot. I am working on a bigger setup but it is slow going so I might have to re-home it soon. Lately I have been thinking that he dosnt do this unless I am there because he thinks I am going to feed him, if I peek around the corner at the tank he is off grazing or chasing other fish around.