Hanna PO4 testing

[Delphinus]

Originally Posted by Aquattro

so, what's the likelihood that my PO4 is actually 0.00? First test with my new kit, and the results are questionable

Which PO4 tester do you have? Hanna does two, one that measures "phosphate" (HI 713 I think?), gives a reading in ppm, and another that does "phosphorous" (HI 736) that gives a reading in ppb (parts per billion). The conversion from ppb P to ppm PO4 is "P * 3.066 / 1000 = PO4."

The 713 is not too difficult to get a zero reading, so, if that's what you have, it's very plausible considering a decent tank maintenance that you describe.

With 736 it's very sensitive and the margin of error at that small a resolution is impossible to get away from, so a zero reading with the 736 is more impressive. I can actually track PO4 fluctuations in my tank using the 736 on an hourly basis ("wow, some fish just took a really large poop.")

With any of the Hanna testers, the likelihood of a false positive is larger than a false negative reading. Ie., a fingerprint, air bubble or particulate in the vial will register as a colour change and give you a higher reading than real. With the 736 you have to really avoid shaking as the microbubbles can take longer than 3 minutes to dissipate.