Dwc cooling

I leave my air pump by an open vent where cool air is being drawn in. This way, my air pump is always pumping cool air into the buckets. Throughout my grow, this has given me a perfect 68°F reservoir. I use hydroguard in case it gets too warm. You can fill plastic bottles will water and freeze them. Then just throw the frozen bottle in your reservoir. This will keep it cool for a few hours at minimum. Twice a day will probably work. Other options include painting your reservoir the brightest white you can to make it reflect light. No, I have not used an ice probe.