Agreed. I have had the same experience.Yeah fresh soil quickly sucks up all the po4 in the water and will do so for about a month then gradually slow down over another couple of months. In the very beginning Ive seen landen and ada zero out 10 ppm in two days. This action operates independently from the soils CEC since PO4 is an anion. Other nutrients that get ab/adsorbed are the cations which is natural. Ive seen the explanation why, somebody here may know, but I dont remember edxactly what happens
In my tanks this is a problem for probably half the species in there. Big leaved green plants are the first to show deficiencies. The first sign is pale splotches beginning on the 2nd or 3rd set of leaves down from the top. Other types of plants display their own weird responses.
Im not sure why its not a common practice to load PO4 with fresh aquasoils. Im pretty sure Dennis doesnt do that, although I havent read a lot of his articles so he may touch on the subject somewhere, idk. And some of these ferts with no NO3 or PO4 Im like how does that work?? I wouldnt for me.
Anyway what I do with a new soil tank is dose an extra 10 ppm PO4 after every water change, which are usually 2x week for a month or so for the ammonia. After 6-7 weeks of 10 ppm I'll give it an extra 5 for another month or so. I dont meticulously test the levels or anything these days, I just add extra approximately on that schedule
Other nutrients I just dose normal from the start, except I may go easy on NO3 for a month or two
Amazing I could dose 10 ppm PO4 and two days later not a trace.
And every time it bottomed out certain plants rebelled. The other thing when it bottomed out was that there was a bloom of hair algae. It was odd as hair algae is something I have never really had to deal with. But it was very repeatable. Zero PO4, hair algae. Toss a large dose in, it went away. It was a battle for the first month or two.
