Who eats ricordea and zoo's

[cag]

Thanks for the replies. To answer the behavior question. The tangs actually get along quite well. Everyone is fat and happy, and there is very little argueing. The occasional showing off and posturing, but nothing that turns into problems. Between a good skimmer and doing a 10% per week water change, the water perameters are usually pretty good. So i think there is something in there snacking at night. The snails look just like the good ones from your suggestions, so it isn't them. There is one worm creature I have seen a couple of times that might be like one of your suggestions. I will watch for it closely. Thanks again for the help.