I have gone the other way for my 10 gal. I have 5 snails in my tank, one very small crab, one shrimp.
Had to get rid of my zebra crab, 5 min after placing the snails in the tank he was right there, turned one over and was in the process of having a snack...
Gone he is, crabs are neat but in my opinion the snails are the best. I put these snails in and I let my glass get a green film on it. Two days later the glass is spottless.
Crabs also are always fighting for others shells, some are mean little buggars.
I will keep the one crab if he does not touch any snails, but I much prefer to have snails and shrimp.
Just my opinion.....:happyfish