I have a 55 gallon tank with 2 clowns and a coral beauty which are going fine. I wanted to add some cleaner crew members in terms of shrimp I had 2 both went missing I added another then gone I think something is eating them. Also I have snails that came in on the live rock along with nassarius snails. Thats it I wanted something to help clean the sand bed along with the algae on the rocks and glass. Thoughts? Also I wanted to add another fish if anyone has a recommendation.