Oh I didn't have any specific cooling liquid so I am using distilled water at the moment?
You will have problems due to the mix of copper and aluminium in the loop. I have no idea over what timescale it will become a problem, but it would be advisable to add an additive or swap out to dedicated coolant which won't have the same problem.
So the provided cooling radiator is copper? That's a surprise.
Because water carries 50% more heat than ethylene glycol, the basic ingredient in most antifreeze coolant, I want to use distilled water (~.68 cents/gallon in Walmart) and perhaps rig up a PVC water filter with the guts from a quality water filter advertising removal of metal ions.
Go with the coolant. What ever you save initially you will pay more in the long run if you don't have coolant or additives if you truly have to go with water.