I tried rubbing his foot, and then rubbing it some more, and a little more and he didn’t budge at all. So then i got the ice cube and all that did was make him move around the rock. I gave up, lifted the rock from the water and he fell right off back into the tank. So I scooped'em up and he’s now residing in my nano.
I don’t know if it was all the rubbing with my finger or the ice cube, but thanks a lot.