Phosphate

[J-P]

I have a Phosphate test kit that I have yet to use, and forgot why I bought it. (I think I purchased it about the same time I started dosing the plants with potassium)

When and why am I supposed to test for it? I searched the Net but didn't get a definate answer.

[CarmenH]

The only time I've used one is when I was trying to pinpoint the cause of a major algae problem...

[RTR]

All plated tank folks use the phosphate test with some regularity, unless they use EI.

Plants and fish and people all require phosphate. In planted tanks, the ratio of nitrogen to phosphorous should be N::P::7-10:1. But note that is by the atomic weight of the N and P alone, not the particular ion which they are one part of. Conventions on relations between fertilizers (which are only N, P, & K in the US -by Fed gov rules) are big points of confusion and misunderstanding.

It creates mass confusion among non-gardeners who must deal with the many requirements of plants, only 3 of which (the macronutrients) are legally ferts, the others are trace elements, or supplements.

Are you aware of the law of limits? If your plants have access to all of their needs but one of the macros, there is no or almost no growth. It matters not if all the others are present in perfect proportions - omit one and you are full stop. That of course results in algae heaven. N & K are both needed in large proportions, but if P is missing, you are in the soup.

The traces and supplements are more likely to have symptomatic distortions and not have vigorous normal growth, but the macros absence or insufficiency is arrest.

HTH

[J-P]

Ohhhh ... not that was a an excellent reply. Exactly what I was looking for!

Thank you!