A quick fix is to put a frozen 2-liter in the rez...I'm not sure the size of your rez, but just monitor it.

:stoned:
DOUGAL25 Reviewed by DOUGAL25 on . High Res Temps My Tri-Meter says my DWC res is 80 degrees. I read in Cervantes Medical Grow Bible that anything over 85 will damage the fine hairs on the roots and cause the plant to wilt and growth to slow. I have plenty of air, 40W worth through four cylindrical 4" air stones and a bubble rope, going to the roots, so if its not getting up to 85 should I still worry about it? So far, the plant is not showing any negative signs, and the roots are still white and thriving as opposed to brown and rotting, Rating: 5