Phosphates - needed?

From: stevensj at calshp_cals.wisc.edu
Date: Wed, 24 May 1995 21:00:38 -0500
Subject: 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?

In response to the same article, we tried increasing the levels of 
phosphate and found that the iron being added as fertilizer (Dupla
drops) caused the phosphate AND iron to percipitate out, reducing the
levels of BOTH and mucking up the water chemistry for weeks after.  

Your results may vary.