Odd Snail Behavior

[RavieReefer]

My Astraea sp. snails have been acting very strange (about the last month). If my snail falls from the glass, they can't flip themselves over. I have to manually flip them over. I even had one, creeping on the sand normally, flip onto its shell in front of my eyes! What in the world would possess them to have such strange behavior? I have had them for a while now, since Oct 08 and I don't recall them doing this before. Perplexed :~

Ph - 8.01
Alk - 3.31 mEq/L
Ca - 400
Mg - 1290

 

[tuberider]

Astrea snails cannot right themselves if they fall on their back, that's why Trochus snails are more suitable for aquariums.