Also, he doesn't look super healthy to me. His mouth looks malformed, maybe from having mbd previously or having it currently. He looks like he needs a lot of warm baths. Get him out in the natural sun as much as you can. He will need a reptisun 10.0 TUBE light running 1/2 to 3/4 of his tank, which should be 4x2x2 (or 18 inches), 40g breeder MINIMUM...but that is really small.
Sorry, after I went back and looked at the pics I felt this was a more urgent situation than I thought at first. He's not in the worst shape I've seen, but he's going to need your help for sure! Glad you have taken on the challenge!