I use UC roots and no chiller. My water temps are about 72. No pythium, no algae, no nothin. UC roots works good.Water temp is crucial in dwc. 68f is considered ideal, 72f ok, 75f+ danger zone. I had to turn on my AC which I was trying to avoid. One heat wave was all it took to light the pythium fuse. Use a liberal dose of the hydroguard and great white bennies. Southern AG GFF is very similar to hydroguard but is literally a million times more concentrated. Ultimately, you have to get the water temp in check. Summer and dwc is bad combo for many.