I have been losing snails in my reef for some inexplicable reason. My water quality has been fine. Today my ammonia and nitrite reading were higher than normal. Ammonia has risen to 0.05 mg/l and nitrite has risen to 0.02 mg/l. I think that is due to some decaying snails that the hermits don't get to. I have also just recently tried some lettuce nudibranchs for the third time. I am not seeing any of them now but there is a slim possibility that they are alive and hiding in the rocks. Anyhow, why would all of my corals, fish and other inverts be doing fine while I am gradually losing my astrea snails. I only use DI water, so there shouldn't be any trace metals in the system. Any input would be appreciated.