Hi oldskinflint. I assume the ice bucket has ice water in it to pump into your reservoir or is the reservoir water just passed through the ice bucket itself? If you are pumping water from the ice bucket into the reservoir, you want to make sure your pH stays okay. Ice will melt and alter pH unless you make pH water to freeze before hand and use that ice. Otherwise, if you are just passing your reservoir water through the ice bucket via a tube, the pH won't really change since the water going in is the same as going out. I have looked at using a PC Water Cooling radiator with fans, or even a peltier cooler to try to keep my temps down but I am always looking for new ideas. I had thought of something similar to this but with the ambient temps outside, the ice would be melting fast and need changing often. Either way, best of luck with it if you do try that and I am interested to see how it works out.