for me I aim for a consistent level, my reef has been at .08 for weeks but my corals (my litmus) is not coloring up the way i want it to. I have other corals that are popping like crazy, but of course the one I want will not.
I just started GFO yesterday in my tank and will measure the po4 here in a bit to make sure im not sucking it out of the water too fast.