Here's the deal I've seen when it comes to the color kits and test strips. Maybe it's just me or I'm going colorblind, it seems difficult to perform these tests without reservations that you may be wrong. Yellow is yellow to me and to identify slight variations of the color seems tedious and accuracy is limited. I just recently started in a hydro kind of setup and I know for a fact going forward I will not keep growing without a accurate PH meter and a TDS meter. I have been lucky so far when it comes to guessing it, but again it's only a guess. I guess a continuation of this question regarding PH, how do people survive a grow with just a color reading of the PH. Is there success in this, and what about TDS?