I use a mix of 2 litres of De-Ionised, distilled and pureified water, 400ml of Castrol Superbike Coolant, and 100ml of Miltons disinfectant.
I run at nothing more than 2'C above room temp, even with a XP1800 overclocked to XP2400 speeds, GPU and N/B, all putting out far more heat than usually recommended