Phosphates - needed?

Hi everyone,  I've been avidly reading the back issues of JAGA and in the
Jan-Feb 94 issue there is an article titled What About Phosphates.  I have
always tried to avoid adding phosphates but after reading that article I'm
wondering if I should - the stuff about plants needing phosphorus made
sense to me.  My phosphates read zero on my test kit (Seachem) and nitrates
are zero too but I know my fish are constantly producing them, it's just
that the plants are using them all up pretty instantly, should I assume
the same with phosphates or start adding them?