From what I've seen and done the mineral has to be moving in order to adequately cool anything serious. (*Imagine the glass tank in a snowbank, I'll look for pictures)
Which means my proper solution would be to re-rig the water cooling units with bigger pumps and pump water straight from the rain barrel. Which means heat exchanger as that water is of questionable quality. Which means WELDING TIME!
It's never a dull moment at Danger labs.
C