That might answer my next question. I was going to go distilled water to start, but my understanding is that doesn't do anything to prevent organic growth at all. Don't want a dirty fishtank in my PC. Retailer I purchased from sent me a free kill coil, which I think addresses this. EKWB says no kill coils in their systems due to metal mix. I'm a little out of my league with the liquid issues and usually end up in someone's argument about whether 1+1 equals 2 or whether 2+0 does when it comes to what to fill the loop with.
Hoping I'm not out of my league with needing to assemble the kit and fill it, but every first time water cooler has to try it the first time I suppose.