I personally have never seen any critter eat enough to make a dent in a diatom bloom.
But,it's a great idea to get some snail in that tank.Nassarius,cerith are a few of my favorites.Just keep in mind,you don't need a whole lot of nassarius snails.You'll mostly want snails that eat film algae like maybe a few turbos.They can be tanks when it comes to knocking over frags,but they do the job.