Landen appears to be sucking up all the PO4 I can feed it. I have been giving it close to 3ppm per day, and every time I test it, PO4 is back to what I call "very zero" where it looks like the 0ppm on the saltwater card, which is yellower than the 0ppm on the freshwater card. I have not been dosing NO3, just KH2PO4 and K2SO4 (and micros). NO3 is down to 5ppm today, and ammonia is down to 1.5ppm. So it looks like I might start dosing NO3.
Saturday was day 0. Sunday, no WC; Monday, 57%WC followed by a 77%WC; Tue, 68%; Wed 57%; Thu 65%. Today, none. Tomorrow is WC day for the other tanks, and I will probably change this one again as well.
Naturally, during my WCs I have had to re-plant some HC and a stem of Cabomba. I am still amazed that there is literally zero dust from this soil during these activities in stark contrast with the Stratum. I'm very curious to see if this continues with age.