Dwc water temp

if you have too difficult to keep your bucket chilled, use hydrogen peroxid (oxyboost, or oxygenated water), it will help you too raise up the oxygen amount in your reservoir, and fight the pythium and all the things which can kill your roots. Few days ago, I had 25°C in my reservoir and my roots was very OK because I add oxygen in my water. In an other xay, try to put your pump in a chiller with ice pack, the pump will take fresh air.

Insulate the reservoir. I have layers of black and white mylar around my buckets and it diffuses light as well as provides an air pocket between the mylar and the bucket for insulation.

68-71 is solid. Put your pump in the coolest spot you can. It will blow chilled air into the res and cool it down a little bit.