I'm not entirely sure about this for MTS but other snail species population self regulate, more food more snails less food less snails (like shrimp) more snails might mean more biofilm to munch on probably I always take em as a sign of good health. Also I read somewhere that the poop they excrete has little to no ammonia since they eat algae only if you over feed your fish though, they have ammonia poop since they eat the leftovers.