My aquatic crab has been sitting nearly motionless for a couple of days. He is alive and is usally quite busy

That'd be my guess

Yeah me maybe ready to molt or something is bothering the crab

Maybe he is sick or sumthin my dads aquatic crabs were like motionless for a few days so we went to the store and they said that they were sick and to make sure you feed them put the food next to them and eventually they will be normal and to change or clean your filters cuz it might be ur water hurting them

u had it for almost 6 mths and it didnt molt before? mine molt once a mth or so.. haha.. as long as it is feeding it should be doing fine.. and yes sometimes mine will become lazy when it was about to molt.. so it shd be doing fine =) cheeros!