Ordering a CUC in Canada?

[muck]

X the Margarita snails as they do poorly longterm in our reefs

Personally I would go with something like this for a 120g... of course the amount of CUC you need is relative to the amount of waste your tank produces.

20 - Blueleg Hermits
10 - Redleg Hermits
20 - Astrea snails
10 - Cerith snails
30 - Red Banded Trochus
10 - Tongan Nassarius (only if you have a sandbed)
1 - Strawberry or Fighting Conch (only if you have a sandbed)