Quote:
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.