Thank you - he would never have come this far without your help and the help of the others. I am extremely grateful!
I will leave the heater on in his tank, but will have to take him out while I'm changing the water/until it heats back up, right? The room I was talking about (with all the windows) gets really hot because it has single pane windows and no obstruction to shadow it (it's right on the Bay). It will be in the 80's again today, so I thought it would be a good place to keep him until his tank heats back up - about 15-20 minutes. I've never changed his big tank, so I'm not exactly sure how to do it.
He actually ate 6 mini pellets. He didn't attack them like he used to, but gobbled them up around the rim of his cup. He really seemed to perk up too. Maybe it was finally eating after so long, but I think being able to get air from the surface so easily helped too. Thanks again for the idea of floating his cup! There was no poop when I left yesterday - I was worried about it sitting in his cup overnight if he did poop. I will check and clean it out first thing when I get to work this morning.
Have a great day. I'll keep you posted on how he's doing. Thanks again!