This continues to amaze me. Admittedly I haven't grown in years, but back in the OverGrow days, I was big on using DWC. At that time, we didn't know all this water temp issues stuff. I remember using SM-90 with my General Hydroponics nutes, and wish I could remember if I used anything else. But I never, ever, checked reservoir temps, and never lost a plant to any root issues. Never had algae either, just tons of healthy white roots. I grew huge plants in 5 gal DWC buckets for years without issue. Now it seems that people spend lots of time chilling their reservoirs, and fighting the things I never had a problem with. Was I just lucky?
It's possible that the SM-90 was what did it for me, but I'm pretty sure that when I first started I wasn't using SM-90. I tended to add those kind of supplements later in an effort to increase yield. I normally averaged between 3 and 4 oz a plant, and some strains could go as high as 6oz. Maybe I'd have had better yields if I knew about proper reservoir temps. But still, I never lost a plant to root issues and I live in the deep south, where temps get quite high.