Why oh why oh why are the 2 shades of orange on the API test card that represent 10 and 20ppm so damn similar? Argubly the most critical test we do and also around the 10 and 20 mark is such a critical cut off point. Do API do a nitrate test kit that tests in single ppm increments where maybe the colours are a lot more determinable, or am i forever going to have to say to myself, "well, today my nitrate reading is 10ppm.......er, hang on, or is that 20ppm", arggghhhh!