Why is my hermit crab burying itself under the water container?

I have 4 hermit crabs together in a tank which I am concerned about. They all cram themselves together in their coconut shack and seem to stay in there all the time except to eat or drink but that's not my main issue right now. My smallest hermit, Shelby, has decided that he is tired of being in the shack or something because he has buried himself under our rock-like water container. He dug himself right to the center of the water container and sealed up his tunnel to there which scared me cause it took a few minutes to find him since I didn't know he was there. He's dug all the way to the bottom of the tank it appears and I haven't seen him come out since. Does this mean he's molting and I should get him into an iso tank so that I don't uncover him in a velnerable state every time I refill the water or is this a sign of something else like he's not happy with something? As I typed this the hummidity is at about 75 and the temp is at 85 with the tank light off in case that info helps.Why is my hermit crab burying itself under the water container?
To my understanding he is preparing for a molting.

(this was my favorite site ever!!)



http://www.hermit-crabs.com/molting.html



"Preparing for the Big Event! Here is my usual procedure for checking for molters. Each day I check on my hermit crabs, and I notice who is digging, who is drinking, eating, etc. When a crab has been attempting to dig a lot, I remove him and examine him for molting signs. Then if I think he may be wanting to molt, I give him a bath in StressCoat庐-treated water. When I bathe most of my crabs, I will tip the crab up on its side and drain out the excess water. Not so with molters. The crabs going into my ISO tank go in there with a shell of water.



When I am at the ISO tank with the molter in my hand, I open the tank and use my finger to swirl a little circular hole into the sand that about as large as the crab. Then I set the crab into the hole. A crab that is truly interested only in molting will dig in and be completely vanished under the substrate in about 1/2 hour. Check on your ISO tank and make sure your crab is dug in. If he is not digging then he may need a protective shield put around him because he is weak or going to molt immediately. An excellent temporary molting shelter for surprise molts is the top half of a 2-liter soda bottle. Take off the bottle cap and discard it. Wash out the bottle well with plain water, dry it and push it into the substrate around the molting crab. Be sure you push it in as far as it will go -- hermit crabs have been known to attempt to dig it up to get at the molting crab. If you use the soda bottle method you might want to put a dark cloth over your crabitat so similate the darkness the crab needs to molt successfully."Why is my hermit crab burying itself under the water container?
Shelby may be moulting. If he hasn't started moulting yet you can move him to an iso. mine like to moult under the water dish or in caves.



The temp in the tank seems a bit high it usually should be between 70-80 they may be hiding out to get out of the heat. Crabs will hide or dig when conditions are too hot or cold.



It isn't all that strange for a crab to spend most of their day in a hiding spot. But usually closer to evening they become more active. Unless they are my large crabs who are active 24/7 because they are silly.