What about taking the rock out of water...he might slide off then..don't know but when you find out let me know..I have to move mine to a different tank soon..he's getting too big.
pull him off...Not rough though, just apply a little pressure for a couple minutes steadily and he should hop right off. If that doesn't work, try setting up a smaller rock right next to his foot and he might move onto it.
Try aiming a PH at him, or holding a baggie of ice water around his foot. He should let go. I wouldn't pull on him. That has never worked for me, and I got stung doing that.
PH is powerhead... point a power head right at him.. r... I just poke around at the foot of mine and slowly wedge my fingers under it and pull it off..
i put mine in an icecream bucket rock and all and left them in there with a little water and they came off on there own. if you do decide to try and take it off your self dont rip the foot or it will die