Thanks for the input, everyone!
I hadn't thought about the heat being an attraction for the top of the tank.........at this time he does not have a heat pad like the others. Maybe I'll borrow the one from my big tank--it's a little large for the 10G but it might still work.
At the moment, Twister doesn't seem interested in eating anything. I noticed that he likes to poke around in the water dish, and since he was found at a pond, I figured he was probably looking for fishies, so I gave him a fishy, and it's still there.
He's most likely still settling in, and here's something else I've wondered:
Since he'd just come out of brumation when I found him ( it was only our 2nd or 3rd warm day) could he be more interested in finding a girlfriend than eating??
I know Deejay's been going absolutely bonkers since I set up the new tank next to her; I think she can smell him. She spends most of her time at that end of her tank watching Twister and crawling up the glass. "Woohoo.......a MAN!!!"
And Twister does seem kind of restless, although he seems to be finished demolishing his home now.
Should I maybe put a little more distance between the tanks??