Hello, I normally used the RSpro NO3 kit, but the LFS was out. So I tried the Salifert, nice and simple. One thing tho, if I look down into the test vial its about 10ppm. If I look through the side of the vial its about 0.25-0.50ppm. I know my tank runs low, normally. But how can we be sure which resolution to use? If I test a friends tank, I wouldn't know which range to use.