Snails dying off

[joec]

After having six trochus snails for 18 months, I've had three die in the last month.

Basic parameters are fine, shrimp is fine

I found them on their side each time

Any ideas why? Did they drown?

 

[AcroNem]

How big are they? They live longer than that, most often when I lose a snail something has eaten it. Hermit crabs do it frequently. Do you have/did you add something that could have?

 

[joec]

They are large. I have no crabs or any other predators like that

I have a Timor wrasse but he pretty much leaves everything alone, he's scared to death of my blood shrimp