Snails

[Richer]

With an up and coming (hopefully) Edmonton livestock order, I'm wondering what kind of snails I should get for my 30 gallon BB tank.

I have two Astrea snails that I see most of the time, either on the glass or on the rocks, and two Cerith snails that I see on occasion at night. Initially, I wanted to get another dozen Astrea snails, but I've been reading up on Trochus snails and now I'm stuck between the two.

Whats the difference between Astrea and Trochus snails? Which would you recommend for a 30 gallon BB tank?

-Richer