You and me both buddy. I'm tripling insulation. Frozen water bottle seem to work really quick, but melts really quick. So the trick really is to maintaining temperatures, not fight if. Even with the water cooler I'll get eventually, this triple insulation will make the chiller work much much less.
You could get wider buckets, pop the whole bucket in, and fill it the outer one with cold water, ice packs etc.
On single buckets its more permissive, I've got them linked, so my measures really are prophylactic than anything
I've got a little 2L DWC going with an AWW lollipop cutting, using Canna Coco nutes :roflcry: from my big plants, totally neglected, zero rez changes only top ups, who knows what temp and pH... man, unbelievable. No cloning gel, nothing, just cut straight to a root riot cube and bubble the water at the same EC as the big flowering plants (EC 1.4 - 1.6) and it sprung into life and just keeps on growing...
Completely neglected, absolutely sure water temps have been above 24oC (79F) maybe more, been almost 2 months, roots are nice and white.
Check this out... I did everything except cut the little air pump. I wanted trouble with in so I could see what it could look like before setting up my alien hydro... Nothing!
https://www.autoflower.org/f119/dwc-using-canna-coco-nutes-yup-you-read-right-26467.html
Just keep the good karma flowin' and 'yer plant will be a-glowin' :KISS:
:High 5: