Found this interesting site:
The author proposes keeping N to P at a certain ratio to prevent algae - recommend an optimal point a N:P = 16 with a lower bound of 10 and upper bound of 22.
At N:P =16, NO3:PO4=23)
Compare to E.I. reference, the N:P is about 2.2:1 (NO3:PO4 = 3.25). So I am not sure how this 16:1 ratio really mean much if most of us following EI already put algae under control.