I've had my RES for over 10 years now.
He's in a 55 gallon aquarium with a fluval FX5 to filter it, the aquarium is generally 77 degrees, he has a turtle topper basking area with a Fluorescent bulb and a mercury vapor bulb, and I feed him the jello shots from this site and occasionally I throw him a few more pellets. He also shares the aquarium with 3 Black Neon Tetras.
He's always been super active, basking all day and even sleeping on his dock he eats like crazy and chases the fish periodically. Seemingly pretty healthy. In the last week though he's become pretty lethargic, just hanging out on the shelf near the water's surface not swimming or basking. He used to chase my finger around and chomp at the glass, but he doesn't do that anymore either. He's still been eating pretty well, but I'm kinda nervous. He would always jump into the water when I got home from work to beg, but now he just sits on his shelf and watches me. I added some water today and he did come to investigate the water addition, which he usually does. But now he's sleeping on the dock with just his head in the water which he's NEVER done... Do you think I need to visit a vet or wait a couple days and see if anything changes?
As far as recent changes to the setup go I had the water temp up to 80 to kill ich that the fish developed and I adjusted the water temp back down maybe 3 weeks ago. I've switched to a new batch of jello shots after running out of my initial batch, is it possible they went bad in the freezer or something? And last it's gotten pretty hot where I live low to mid 90's, maybe he's just hot so he's staying in the water more? That also kind of explains the head dunk thing. And the last change I made is I just switched the fluorescent bulb to from 100w to 60w and I turned off the mercury bulb to see if heat was the issue. And again he's now basking...