Help!!

[elm0]

I'm not sure whats going on but it seems like all my red and blue legged hermits and all my turbo snails, seem to be dead for several days now. I thik the crabs are still alive but they stay inside their shells and havent moved in days, on large red leg crawled out of his shell and has layed in one spot, barely moving for days now. All the snails just retracting into their shells and stopped moving. All the fish seem fine. Any ideas on what i can do?

 

[cprdnick]

What are you water parameters?
PH and salinity are a major thing to watch when it comes to inverts.
Tell us:
PH
Ammonia
Nitrite
Nitrate
SG
Temp
Other inhabitants of the tank
Substrate, and anything else that you think might be important.

 

[overanalyzer]

pick up a snail and smell it - if it is one of hte raunchiest smells you have ever encountered then get it out of yoru tank (it is dead) and check every snail.
Also - what are your calcium and alk measures as well as those others mentioned?