I have never used a chiller, and the only time I ever had an issue with root rot was when trying to do it in a 5 gallon bucket a hydro store suggested. A BLACK bucket at that, which of course absorbs the heat....really baffles me why they would choose black instead of white for a DWC bucket. Anyhow, the volume of water in it was too small, more susceptible to warming up. It was only in a tiny 3x3 tent with a 315w CMH as well. Anyhow, after that I ditched the bucket and went back to bigger volumes of water in totes. The best thing for DWC really is to have a large volume of water, like a large reservoir you would use to feed an ebb and flow table. Put some bristol board over the top, cut some holes...voila.