Maybe just my own observation, but I find mixing snails with crabs is counter productive..Unless you are the one selling these critters. The crabs have a nasty habit of yanking the snails out of thier shells if they get turned over (And they will) for a nice snack. I have no crabs in my 10g or 75g. Snails only and I have had far longer survival rates. It gives me enough time to turn over any snails that are unable to right themselves without having to worry with crabs getting to them 1st. astrea are the worst, with margaritas in 2nd place and turbos in 3rd. (least to most likely to right themselves) However, astreas seem to be the most tolerant of temp/sg
changes. Whatever you decide, I would try some snails first and see how it goes before you dump a but load of $$ into a 'cleaner package'. Consider also, you may not want some of the other critters that come with some packages. Read up on all animals they want to send you bfore hand..