That is a good question, here is a litlle back ground. If your grow room temps's are around 89 to 95 during the day, and your res is in that room. Then evenetualy the water in the res would get above 72 and we all khow that is when alge and othrer slimy type creatures appear. So if we had a chiller that could get the temp to stay 68 alll the time the no more problems with elge and stuff. If I had the room I would move the res out of the room but this is not an option. A res chiller can cool and keep cool an amount of water at a surtain flow rate from 30 to 10 degrees,it all depends on the flow rate of the pump and the size of the chiller. Hope that helped, I am getting tiered of the frozzen bottle way and it's not even the end of MAY.......:thumbsup: