Phosphates

[djlen]

How many of you test regularly for Phosphates, and how important is it to do this test? What is a good, accurate phosphate test kit?
Len

[plantbrain]

I, like many folks, never obsessed over PO4. Then, due to my excellent plant growth, folks started bugging me about it. They were adding all the same things though my tap water was slightly harder and it had lots of PO4's.

I've measured it critically for a number of years in different systems.
A good kit and the ones I used during this time were Hach and Lamott. These cost 50-90$.

Do you or an average hobbyist need these? No. Most kits like a SeaChem PO4 kits do the job.

PO4 as a parameter only needs to be present to satistfy the plant's needs, which can be quite high. I've measured up to 0.4ppm of PO4 removed per day and 0.2ppm removed ina few hours(6). 0.2ppm per day is enough for a good average usage in a thriving aquarium.

You can get away with less or more. It's okay to run the tank down to zero for 1-2 days. So dosing 2X a week in a well lit, CO2 enrich fully planted tank is fine.
You are hitting a large target here. No need for precise control.

The test kits are good enough for presence or absense. If you are out normally, you'll need to add some PO4 2-3x a week is all.

A water change at week's end will remove any build up etc( and NO3, and any other gunk as well).

Not an issue as long as there's some present most of the time basically. Careful in assuming the lower values, say in the 0.3ppm or less range, especially if they do not move with the test kit. They(PO4) should be remove
in 1-3 day's time and if not, reassess your nutrients like CO2, NO3, K, traces.

Regards,
Tom Barr