why do my fish attack inverts

Question
Hi,
I have a 30 gallon FOWLR with one percula clownfish, one yellow watchman goby, and one strawberry psuedochromis. I feed a mix of brine shrimp and marine cuisine 2x day and every third day add an extra feeding of mysis shrimp or squid. However, my fish relentless attack the snails and hermits. I have seen the goby  knock a hermit over, grab the shell, and disappear into her burrow. The other two attack hermits and snails but I have never seen them actually eating them. I bought 15 blue legs hermits two weeks ago and most are gone. Is this behavior normal? I have increased feeding to 3/day but nitrates went up, so I decreased. I do 10% water change once a week. Any suggestions? Thanks

Answer
Hi Lauren. It is not normal behavior for any of these fish to be attacking and eating your snails and hermit crabs. With that said there are always going to be different personality traits within the same species of fish. If your fish are just knocking the snails and hermits around it may be due to their territorial nature. Sometimes a fish can be very territorial to the point where anything that happens to venture into that said territory will be swiftly moved away or knocked into. None of the fish you have are supposed to eat them though. Have you looked into the possibility of something else killing the inverts in your tank? Copper is one culprit that often comes in with the water supply and is toxic to inverts. You may want to check it just to rule it out. Chances are there is something else going on in your tank that may be causing the hermit crabs to die and then they become food. Check all your levels and make sure the hermits are getting enough food and that there is an ample algae supply for your snails. If everything checks out then I would say that you may have just one of those fish that doesn't fit  the "typical" description of the species!