Water Water every where, at 32 d.f. If you want to get more cold for the buck. Add sugar to the water in the 2 liter bottle. Thats what in cooler ,coolers. NOTE leave room for expansion.
Always use a air stone in you resivore, plus a mixing pump, any real small pump to mix the fluid for 15 minutes prior to filling you buckets.
I use a automated system using a 74 printer port relay and relayrunner program for my grows