Based on that info, here is what I would roughly get:

For the 90

140 Dwarf Ceriths
35 Florida Ceriths
?? Nassarius Snails (depends on # of fish- maybe start with 15 and go from there)
20 Limpets (Express Mail)
1 Chiton (Express)

I would get a better idea though if you filled out this form:
Custom Clean Up Crews

Lots of questions I am afraid.