Vicious_Fish;1520097; said:Well if I were you I would go out and buy an aquarium heater and a UVB basking lamp ASAP or he will probably die from pneumonia. What you can do till then is put him in a box with a heating pad underneath it. Just make sure it doesn't get too hot and cook him.
Here's a good care sheet for RES that I think you should check out.
http://www.austinsturtlepage.com/Care/caresheet-red_ear_slider.htm