Am I testing PO4 correctly?

[ReefSentinel]

 

[fishchef]

What brand of test are you using, Salifert? Many years ago I used Salifert. You are better off with a Hanna Checker. Even though they have their problems, when your trying to read an accurate zero the color charts can be miss leading.
I was getting a zero all the time with Salifert and on a Lab Grade Hanna at my LFS it was actually .50 ppm PO4. At least the Checker is in the ballpark.

 

[kurt_n]

Yup... that's Salifert.

I'd read that in the 0.1-0.2 range. But along the lines of what fishchef said, with the ranges given in that Salifert test kit, and the subtle changes between colors, I've always taken *any* tinge of blue as a bad thing when I've use them.

 

[fishchef]

Yes, you might be doing the test correctly, but the overall reading has too much room for interpretation. We're not test crazy and when they're done an accurate number is the best +/- any variable.

 

[Dan_P]

You are taking the reading correctly. At the lower range, it gets tough to make a call.

The absolute number is not as important as whether is it increasing (not so good) or decreasing (good).

 

[fishchef]

Yes, If your seeing color at all that's bad. My concern was that I was getting no color at all and my PO4 was way high. The Checker gave me a numeric reading that was more useful.