I had no confidence in my ability to accurately test for PH using the Taylor color block test. Am now using a Apera Instruments PH60 tester. Love the accuracy and no-nonsense digital readout. I calibrate it about once a week but that's seeming like overkill, it hasn't ever been off more than .02. I've seen where PH tests are inaccurate with FC levels higher than 10. Does this apply to just the Taylor color block test and similar, or does that apply to the electronic testers like the one I'm using also?