The Growonix Cold Water High Flow Membranes for purifying water with reverse osmosis are specially designed to perform even when fed with cold water. Most reverse osmosis membranes have dramatically reduced output when used to purify water with a ratio of waste water to pure water that is through the roof. The Growonix high flow cold water membrane has an output of pure water of 150gpd in winter with cold water in the 40s and an output as high as 230gpd when incoming feed water has a temperature in the 70s in warmer weather. Even at that flowrate the Growonix Cold Water High Flow membranes still maintain a 98% rejection rate and a constant 2:1 ratio of waste to pure water. Growonix is currently working on a reverse osmosis unit for the aquarium hobby but in the meantime you can stock your existing R.O. with one of their high flow cod water membranes so you can have high water production all year long.