O.k.
First. He needs a place to hall out of the water and get dry. A basking site is a MUST for RES.
I suggest a HOT site...I give my guy a basking spot with temps from around 88-105 degrees. He utilizes this big time. They need time to bask and dry off 100% or skin conditions can happen. He will also need UV light over his basking site.
Adults need minimum 55 gallons as a full time home.
<img src="http://8snakes.myftp.org/marisa/Reptiles/mikey/pond.jpg">
That's my RES summer home for my male RES Mikey. In the winter he lives in a large rubbermaid. In the summer home he doens't have a consistant temp or anything, but the UV he gets makes up for it and generally Ontario summers are overall warm enough to support him.
Marisa