Sounds like it's working well Glen(?)
For the record, Ryan Erickson gets credit for this. I read something he posted awhile back and picked his brain about it. He wrote about adding NO3, and while talking with Jon @ J&L he suggested Seachem's Nitrogen. Ryan may have also mentioned it, but I don't recall ... it was last year
@ Tang Daddy;
I used Seachem Nitrogen and had no issues due to their product. I did add too much too fast though. This dropped my PO4 so quickly that my corals were a bit PO'd for some time after.
And for everyone;
Looking back through my records, I started dosing 2ml/day back in early November. Nothing happened for days so I bumped it to 5ml/day. Couple days later I finally read 5ppm NO3. PO4 dropped from 0.06 to 0.03. A week later NO3 was up to 10 and PO4 was 0. Then the tissue recession and bleaching started ...
Had I known there would be such a drastic effect I would have tested daily.
I pulled my GFO and PO4 rose back to 0.04. I continued to test/dose until PO4 was stable, then stopped dosing. I also pulled my Carbon.
This was early January and I haven't dosed any Nitrogen since.
March 30th Hanna told me PO4 is @ 0.01 and Salifert reported 0ppm NO3.
It's been 2 weeks since a 25% WC (due tonight) and I just tested before another WC;
PO4 is @ 0.03 and NO3 is @ 0ppm.
Currently I only have 4 fish in the DT, plus a couple shrimps and some hermies. They are fed pellets for lunch, and I rotate between 2 different kinds of flakes or a cube of frozen for dinner. Plus nori a couple times a week. When I feed, it's like it's snowing in the tank so there should be higher readings ...

If I feed them any more they'll pop !!
I have some fish in QT and will be doubling my fish load in the near future. This will cause some new testing/dosing, but I hope it will help increase my levels enough to get some NO3 and PO4 readings without having to tweak things too much.
Hope this helps someone, and good luck Glen