I used to have a big (watermelon sized) blood parrot that would swallow big ramshorn snails whole. idk if this is good for them but my fish never had any ill effects, i think midas do that In the wild.
Ive had midas babies tear the snails out of the shells but never eat them shell and all like my big parrot did.
I've heard that cichlids keep animal grit from insect shells etc in their gallbladder in order to grind up food, so that a diet without hard shelled insects occasionally (eg crickets) is unhealthy for them.
I wouldn't feed him snails all the time, but i doubt it will kill the fish.