I believe I did three water changes during the 60 days I treated the tank. Nitrates are currently around 15ppm, down 75% from what they were.
So they did go up a little, but not nearly what they were. And I suppose if I really wanted to, I could repeat the treatment a second time at the normal recommended rate of dosing without fearing the consequences, now that the nitrates are at a much lower level.
However, at this point I'm thinking about a DIY denitrifier that I read about in Reef Discussion.
I do not use mechanical filtration. DSB, Refugium, Skimmer, LR - that's my filtration.