If you put the water on the heat side (in a heat safe container!) it'll help keep the humidity up, but your water will evaporate a bit quicker. Since I wanted the humidity, I put mine on the heat side, but I have those clay balls, and dirt, between it and the bowl. I also put some polished stones in the bottom of the container. I'm using a food grade microwaveable glass bowl for his pond. He seems to like it, and the rocks make it easier for him to hop out.

Hopefully your friend perks up soon! If you get really worried (and brave) you can slap a SMALL amount of baby food (chicken or turkey) on his lips. He'll lick it off, and it'll give him some protein. I do that to my gecko occasionally when he's in an eating slum, and it seems to help perk up his appetite. It pisses him off though, and he doesn't have teeth, so... decide how much you like your fingers first.