Sails and Hermits dying
 

A friend of mine has a fish only salt tank. He is having trouble keeping his snails and hermits alive. I cant seem to find out what is wrong with his tank
All his water parameters are good, salinity is good, temp is fine.
For fish he has a yellow tang, a foxface, a tomato clown and 2 damsel fish

What could be wrong??

missing
 

is their any chance their is a bad crab in their or a mantis
might want to watch the tank a night! just my $0.02

Copper perhaps?

No I am positive there is none.

should there be some??

There should be NONE. Copper is lethal to all inverts (corals, mollusks, etc).

copper is often used as a medication in FO tanks, but is deadly to all inverts. If he's ever medicated with copper to cure ich or something there may be traces of copper left that are enough to kill his inverts.

What kinds of fish are in this tank? Might they find snails and hermits as nice midnight snacks?

What is his salinity at.

Fish are
yellow tang, a foxface, a tomato clown and 2 damsel fish

salinity is at 32
He has never had a fish illness so i know he has not used copper.

could it be he had a bad batch of snails and hermits?
I had the same problem with my tank when i first started it. 3 months into it I bought 5 snails put them in and a week later none were alive. Now they are breeding like crazy. mabe i should just get him to get 5 more of each and maybe they will be fine.