oh and FYI, you would need to clean every component COMPLETELY with demin water before installing and maintain the system in a clean environment (even with an ion exchanger). I would keep a conductivity meter in the water and make sure it stayed below .2 umho/cm^2 (that's really clean!). Any water lost to evaporation would need to be changed, and if your conductivity increased you would have to change the demineralizer resin. (and PLEASE make sure its H-OH resin and not like NH4-OH resin).
I would say run all fans in the case at a low constant speed, and have a variable speed fan to cool the entire water volume (to air) that doesn't kick on until the water gets to like 40*c. 10% speed at 40*, 50% @ 45*, 100% at 50*. That would keep any chip below its failure spec by a safe margin I think. If you were really OC'in a chip, maybe maintain those temps lower. Any thoughts?