Not sure what is going on. I have had my 120 up for maybe 8 months maybe 10. Recently my snails have been dying. I tested ammonia and its zero. I did have a problem with some "reef safe" medication a while back that killed a lot of my crabs. I was using Melafix and Pimafx so they could have been the cause. But Rally Pro is supposed to be invert and coral safe. I read another post where a guy said it wiped out half of his crabs. But that was quite awhile ago I used it. Crabs aren't dying. Water has been changed. These are Mexican Turbos dying. Also my Trochus snail died. I just did a big water change. Just in case. Any ideas? They could have fallen. I found one on its back. I righted it and it went to the glass but it died a few hours later. The one I saw in the back is in its back also. I read Trochus snails sometimes can have trouble getting off their backs even though usually that is not a problem.