First time aquarium owner

[Mandalitta2012]

I have a question about my crab, I have had him for about a month now and he molted a few days ago and has been fine. This morning I woke up and he was laying on his back after my nephew turned the filter off and then back on a few minutes later. After he did that the crab has barely moved and seems to be dead most of the time until we go to pull him out. I am not sure if him falling off the plant when the filter went back on or something else is causing him to be like this. He hasn't really moved from the bottom of the tank all day and he normally stays away from the other fish, but he isn't bothering with them. I don't know if he is still molting or if there is something seriously wrong with him.
Mandi

 

[Hholly]

Is it a salt water or fresh water crab? There are unhealthy fish sections of the forum for each. Good luck.