The Salifert test will actually go down to 0.2ppm. If you read the color through the side of the container you divide the color scale that comes with it by 10 - so the lightest shade is 0.2ppm. If you read the color looking down from the top, you use the scale as it is - so the lightest shade is 2.0ppm.
Just a heads up for when you get the kit!
Oh... and I agree - 0.0 is the "ideal" for nitrates. But that's not going to happen because you're going to pick up a trace amount from your salt mix. Even though Reef Crystals is "nitrate-free" I consistently test it between 0.2 and 0.5 ppm
, starting out with DI
(0.0ppm nitrates) source water. Also agree that magnesium should be OK if you're doing 20% water changes every week. I've seen various targets for magnesium, but the one I use seems easiest to remember... your magnesium should be 3x your calcium levels. So if you're running 400 ppm
calcium, shoot for 1200 ppm
magnesium. Of course, those are "round about" numbers! Think my last test numbers were 1160ppm, with around 400 ppm