hi all i am planing on getting a passive radiator for a core 2 quad q6600 and a zotac 9300 itx plus dont know what graphics card as of yet maybe a gtx 460 or a gtx 580, plan is all about taking the heat from the pc and dumping it into the living room as i plan on geting a alphacool hf passive radiator just need a help of choice on the the radiator size for the graphics cards
With aluminum radiators and almost all cpu/gpu/chipset blocks being copper you will have galvanic corrosion. You should aim to have only a single metal type in a loop or you'll need some chemical inhibitor.
Also save some money use distilled water off the shelf. 4€ a liter is just excessive.
Galvanic corrosion, like posted above by d0gr0ck. Google it. Koolance used to have a lot of issues with their radiators in the past. Those rads you linked are aluminum...mix that with copper water blocks, bad things happen over the course of several months unless you have coolant that suppresses corrosion. You could go cheap and do a mix of automotive coolant and water, but you are likely not going to get good enough cooling to be passive for your setup.
Just use distilled water from any grocery store. It's very cheap, unless you actually plan on running mixed-metals in your loop. If so, consider some easy-to-find glycol coolant to mix...I'd say 25% coolant to 75% water...shouldn't need more than that. But, you'll want to flush your loop every few month and keep a close eye on corrosion. It's likely you won't see much of an issue with it, but I'd rather not take chances, honestly.
I'd avoid radiators (or any component for that matter) with aluminum if at all possible:
1. Copper is a much better heat conductor
2. Aluminium will cause corrosion.