OK, Hi Clint, lots of info now and looking much better...
Nitrate(NO3) of 40ppm in the tap water, rather than it being nitrite(NO2) is what I suspected and I'm glad we've confirmed that. The nitrate being there will not be a problem, whereas the nitrite(NO2, being a much more serious poison, would! So no problem in the tap water department as far as our fishless cycle goes.
OK, so carbonate hardness (also known as temporary hardness, a term you may have heard) is the thing measured when we use the term "KH" (which stands for the german words for carbonate hardness I believe) and the whole reason we talk in german degree terms a lot is because when you do the typical "drop" (as in dripping one drop of test reagent into the testtube at a time) test you are literally counting up your german degrees right then and there! If you drip in 17 drops to get to the color change, then you have 17 degrees of hardness, no calculations needed. Its that easy. And it holds true for both GH and KH tests (but with different reagents of course.
A KH=17 reading is totally the opposite of a KH=0 reading, so its good we've cleared this up. Your KH is good and solid and will help you maintain a steady pH. It means the pH will be less likely to rapidly drop once the fishless cycling causes Nitrate(NO3) to be high. This is all good.
Finally, the Tetratec EX600 is a very good EC filter and the media they start you off with are good so I'd just leave them the way they are. That's good too!
So does that leave us with any questions?
~~waterdrop~~