po4 test kit

[d0ughb0y]

for the po4 test, should the starting color be the light yellow color?
I know for the nitrate test, I get the starting color of light blue, then start to go lighter and proceed to the next color in the wheel.

but for my po4 test, the color seems to be always about between the 0.04 and 0.08 color, and stays that way. does it look like I have a bad po4 test kit?
I know I get that result using tank water and newly mixed salt water. I think I got the same result using rodi, but I can test that again, and I can test tap water as well.
at a minimum I was expecting the starting color to be light yellow, but I never get that color.

[d0ughb0y]

I just watched the po4 test video, and the color I get, is always like the end color shown in the video. Meaning, I never get the starting color then slowly progress to the end color after 6 minutes. Now the video never showed the starting color, so I am not sure if it started from the light yellow then progressed to the end color, or if during the whole 6 minutes the vial color was already the end color.

[RedSea Aviad]

Hi d0ughb0y,
The reaction start color depends on the PO4 concentration.
The more PO4 you have in the water, the more Blue-Green the start color you will be at.
I helped a customer who had PO4 levels so high, that as soon as he added reagent B the color was already at 0.64ppm.
A few things might affect the results:
If the vials were washed with soap- the residual soap can cause higher reading than it really is.
Sometimes if the reagent dropper bottle is held a bit to the side, and not 100% vertical, the drop will squirt out with some air and it will affect the reading.

Keep me posted!
Have a nice day,
Aviad.