I was lucky to find TFP fairly early on. I became suspicious of the pool store on our second trip, when the brand new employee behind the counter had to keep redoing the test because he was clueless. After that, we took a sample across the street to other pool store, where we were given wildly different numbers and a 7 page printout of the various chemicals we needed.

I left there empty handed and good thing because if I had listened, we surely would have had to drain the pool. After brief misadventure with a pool service that turned out to be a bunch of lying liars that lied, I found TFP and never looked back.
Thanks to TFP, I finally understood why I needed to keep adding acid and figured out why I was holding chlorine with the SWCG. I followed the SLAM and my pool water turned the color I had been expecting, instead of the weird greenish hue that everyone kept saying was fine. Now my water is crystal clear and feels amazing!
On my last trip to a pool store to stock up on acid (they are the cheapest), I overheard the employee telling someone that “chlorine won’t kill algae, it only bleaches it out so you can’t see it. Only algaecide kills algae!“ It was all I could do not to interject!