A year ago when I upgraded tanks I bought a bunch of Cerinths, dwarf Cerinths and a few nassarius from reefcleaners. Now they are mostly all gone. No hermits to kill them and all other inverts are alive and healthy. Over the last two months I've recieved several email solicitations from reefcleaners to "replenish my CUC". I assume this means a large amount of die-off is expected. True? And why? One would think snails would be some of the hardiest creatures in our tanks.