I dont know of any snails that will eat the coraline, Urchins will eat it.
What type of fish are you getting? If you are getting fish that will eat them then no reason to get them.
Get a mix of hermits and snails start out with a small number in a new tank because there may not be a a lot of food for them.
A 12-24 hermits and 12-24 snails. If you get Turbos only get a few 3-5 they are big and need lots of food. I got a mix of snails in my tanks, astraea, turbo, red stripe, nassarius,nerite, ceriths. Stay away from the bumblebee snails, they will eat other snails.