Can my Hanna phos checker be off?

saltysailor · Nov 5, 2020

Hi all, I got a Hanna phos checker second hand from a fellow hobbyist. All of the packets he gave me were up to date and was tracking my phos fine. I ran out and ordered the same kind and double checked to make sure they were the same. When I got it I kept getting readings of 0.00 which was highly concerning. I didn’t think that was impossible so I started feeding more but I could see algae growing. I’m confused.

saturn13 · Nov 5, 2020

saltysailor said:
Hi all, I got a Hanna phos checker second hand from a fellow hobbyist. All of the packets he gave me were up to date and was tracking my phos fine. I ran out and ordered the same kind and double checked to make sure they were the same. When I got it I kept getting readings of 0.00 which was highly concerning. I didn’t think that was impossible so I started feeding more but I could see algae growing. I’m confused.

I've gotten the same, re-ran the test immediately with the same vials and get a different reading. One thing I make sure of now is the vials are smudge free, and micro bubble free. Checking this has increased accuracy. If you know your tap pre-rodi has phosphate, you can atleast test that and see if you are getting a reading. If you get 0.00 there then it might be the checker.

saltysailor · Nov 6, 2020

saturn13 said:
I've gotten the same, re-ran the test immediately with the same vials and get a different reading. One thing I make sure of now is the vials are smudge free, and micro bubble free. Checking this has increased accuracy. If you know your tap pre-rodi has phosphate, you can atleast test that and see if you are getting a reading. If you get 0.00 there then it might be the checker.

If it were the checker how would I correct? It has given a reading of above 0.00 since. I just still see algae growth...

saturn13 · Nov 6, 2020

The only thing I know of is calibration, https://www.hannainst.com/hi713-11-phosphate-low-range-checker-calibration-set.html
If there is anything more that can br done I'd suggest Hanna's customer service.

Randy Holmes-Farley · Nov 6, 2020

saturn13 said:
The only thing I know of is calibration, https://www.hannainst.com/hi713-11-phosphate-low-range-checker-calibration-set.html
If there is anything more that can br done I'd suggest Hanna's customer service.

To be clear, that "calibration" fluid is not very useful, IMO. All it checks is that the electronics are working correctly.

Far more useful would be a phosphate standard that actually checked the reagents, the cuvettes, and the user methodology.

Randy Holmes-Farley · Nov 6, 2020

saltysailor said:
Hi all, I got a Hanna phos checker second hand from a fellow hobbyist. All of the packets he gave me were up to date and was tracking my phos fine. I ran out and ordered the same kind and double checked to make sure they were the same. When I got it I kept getting readings of 0.00 which was highly concerning. I didn’t think that was impossible so I started feeding more but I could see algae growing. I’m confused.

Which checker?

If the HI713, that 0 ppm could really be anything from 0.00 to 0.04 ppm, according to the specs.