Thanks. I'll try your technique this weekend.
Just FYI, I did the 25% water change last night, just two days after the last one, and my Nitrates did not budge. I'll call it 20 ppm
since the color matches the card, just darker. I've come to the conclusion that's just what I get and I'll have to be extra vigilant with water changes, which I would be anyway. I'm not going to open a thread on this.