as title says, one of my nerites has been excessively shy lately. a friend of mine who also keeps fish and nerites came over tonight and glanced at him. she says its not normal... but since ive had him for about 4 months already, i know that hes always been shy, rarely moving too much (at least during the day), but still out and about. however for the past 2-3 days hes kept his trapdoor closed and he hasnt been moving. i know hes still alive, since hes resisting when gently i try to pull on his trapdoor. is this normal behavior? i know snails can decide to hibernate and come out after a period of time,, but this kinda worries me..