I don't think I mentioned anything about Chlorine. He is asking for a way to cool the resevoir water down without a chiller. I tried to find the thread that I read on another site but several people tried the fan thingy on the res water and all reported reduction in water tempature by 10 degrees or better. I tried it on my 50 gal resevoir and it did indeed reduce the tempature of the water. I will try to find the thread . It even explains techniquely how the hot air outside the res doesn't keep the fan from cooling the water . It is interesting stuff for those who may not be able to afford a chiller .