I dont understand Red Sea. If from what I have read is correct, its the KH that sets what co2 level the indicator will be green (30ppm w/KH=4, 40ppm w/KH=5) etc. So why do they just indicate problem with accuracy with KH under 4? What about over 4? And also they should stress the importance of using something like distilled water or RO water, since tap water and tank water both can have other buffers present. I also like the idea of dilluting the KH solution 50% so you can measure in .5 degree increments rather than 1 degree.