Before we go any further I think I should state that my tank was/is a dirt tank with an inert cap. C02 @ 1bpm for 8 hours a day. I understand Tom Barr has his approach but it isn't one I chose to follow. My phosphates are high from the tap and when measured literally off the chart. My nitrates before going dirt registered at about 5-15ppm (usually 10ppm) before the weekly water change. My water is teaming with organics. Sometimes it comes out looking as white is milk. Will sit a fizz for a good 5 minutes after leaving the tap. At times my water has a mirky brown in appearance and a distinct smell. I should state that I test my water weekly (I like to keep notes on it even though they mostly remain uniform) I use both api and nutrafin. Personally I prefer nutrafin as the base reading is always clear/water so even barely readable amounts will show up if present.
NPK and nitrates in my tank spells disaster. lol I once read a thread on tom barrs forum where he mixed up a cup of nitrates and poured it in. If I did the same for my tank then I'm pretty sure within a week it'd turn fluorescent pink. Yup that is an exaggeration but best illustrates my point.
There is more than one approach to this hobby of ours. Tom Barr's is one I respect but simply can not follow.