Should I get the Phosphurous Checker?

[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.