Should I get the Phosphurous Checker?

[lastlight]

the Lastlight Checker Holder© is fully compatible with both Hanna models. comes complete with removable and washable funnel.

[asylumdown]

Brett, there are times when life gets busy and I get all distracted, and just for the tiniest moment I forget that you're my hero.

Then you remind me.

[tytown]

Ok, feeling better about it tonight. I went at it again but with the approach based on people's comments and some other research and was able to get a spread of readings within the units rated accuracy +-0.03 ppm (+-5% of range; range =200 PPb)
I perfectly prepped the reagent packet to ensure that it would all get in the vial before the test is even started
Grabbed water from the same location in the tank being careful not to get finger water in the sample.
I kept the orientation of the vial the same throughout all tests (10ml facing me)
And I used a fresh microfibre cloth and meticulously buffed the outside of the vial.
After all that it tells me I have 0.09 - 0.12 ppm PO4.
I would have liked to know which of the above had the largest influence on the results and I wonder what my readings would have been if the vial was flipped 180. Unfortunately I can't debunk the errors I went through becuase I only have 4 reagent packs left from my box of 25 bought just yesterday.
I'll use the current levels as a reference from here on out.
Thanks everyone.

[asylumdown]

If you have access to one, might be nice to test with one of the PO4 hanna's as well. The other thing I would find is that my ULR kit, when converted to ppm, seemed incapable of returning a result much below 0.08, while the regular kit would return 0.00.

If both the regular range and ULR kits agree that your PO4 is in the 0.09 to 0.12 range, then your method probably worked and you can have a higher degree of confidence in your results.

[lastlight]

The lowest reading I've gotten with mine is 0.02 but I've often got 0.04.

And thx Adam when can I expect your order? Kids are wondering how many more units they have to build tonight before I give them water and rest.

[MitchM]

I also use the ULR checker but I don't use it for accurate numbers, only trends.
I use a target of 10ppb though to adjust my Foz Down dosing.
I also take the appearance of the tank to tell me what's what.