hello lately i have noticed these little polyp like things kn my rock and conch snails but I dont know if they are bad or harmful for my tanks environment.
I wouldn't worry tbh some may disagree but if you don't have them on your glass then it minimal some species will grow like the ones you have if you dont like them take the crab out put it in a cup of tank water scrub them off then put it back.
Oh, and toss the cup water down the drain lol