More than likely the Sea Hare had died,and the snails started taking care of the remains.Nassarius snails are omnivorous.I recently had one of my big Zebra turbos die for no apparent reason.The hermits were eating the snail,and the Nassarius were right in the mix of things, not even bothered by the crabs!Also,kind of strange is that they would even eat the thing.I would have thought that the Sea Hare would not taste too good,and maybe even be toxic to them.