Check this out, it comes with a built in pump. It may not be too powerful, but it would accelerate the water. Especially within the resevoir, I imagine it would improve temps slightly and flow rate a good amount.
http://www.aquastealth.com/index.asp?PageAction=VIEWPROD&ProdID=35
http://www.aquastealth.com/index.asp?PageAction=VIEWPROD&ProdID=35