How to keep RDWC water cool!?

Hmmm. It's hard pal without a water cooler. With tents the ambient temp can't be above 23-24% without running a sterile tank. So, if you water exceeds 20c..don't use organic nutrients and look for someone to grow in sterile tanks. I used h202 my water temp was like 25-28c. Needed to change every few days. And it kills organic matter. Including roots. So. I'd advise getting something premade A water cooler is about 200e, if you have issues. Just grow in coco/clay pebbles etc. And do DWC in winter. (If u hv 1) Good luck

I used to throw frozen water bottles in my rez back when I used HPS lights. Just rinse and refreeze when you replace them.