Funny you posted those as that's what some are using. or some other stuff planted tank guys use that sort of green looking, but is potassium nitrate. if I had a link readily available I would post it.
I've had FW tanks my entire life, but never went into the high end planted route. My current FW tank is only 20G with 2 angels, a bubbler, and a HOB filter.
I keep my FW tank super KISS. Don't think I've ever done a WC on it, and I add RO/DI as topoff. I've had these angels current for about 6 years. Been doing RO/DI topoffs since I started a reef tank 4 years ago.
I used this CALC to figure out my mixture and dosing amount for exactly 2ppm. You have probably seen it.
http://www.theplantedtank.co.uk/calculator.htm
Worked perfectly. I figured out I needed 34grams of stump remover added to 485ML of water, and 15ml added tot he tank for a perfect 2ppm.
Dosed last night, came out to 2ppm. Checked today and back to 0 with no drop in PO4. From what I've read this is normal as your filling up the things that were nitrate depleted before(bacteria). Just dosed again and will check level in an hour or so.
Anecdotally, things do look happier today and my 2 euphyllia are as big as I have ever seen them in my tank. That hammer I bought down at your guys place Soul, shrunk up to half it size, but today is just as full if not fuller then when we saw it in the shop.
Feels really odd to be adding something most people are trying to get rid of.