Trochus snail keeps falling on back

[jbonez_]

I recently bought two trochus snails two days ago, while the other one is doing fine this other one keeps falling on his back, since Saturday I have righted him 15+ times, he can't seem to right himself. I put him on the rocks and he falls off, I put him on the sand bed and I come back and he is somehow flipped again unable to right himself. What is going on here?

I need to go back to my LFS and grab two more snails for algae this weekend, what kind would you recommend for a 20g? Also, is there any type of Conch I could get for my tank? I would like something that cleans my sand bed.

 

[SimbaAnto]

Nassarius snails would be great for cleaning sand bed