Hanna ULR our to lunch?

[Semisonyx]

For the longest my Hanna Phosphorus has been reading in the 7-17ppb neighborhood. I’ve been dosing nitrates to get detectable numbers due to poor growth and coloration. I’ve been waiting for my po4 to correspond and drop due to bacterial consumption of nutrients being limited by NO3. After a couple of weeks of getting 2ppm NO3, last night my PO4 read 0 on the Hanna.

Per the planted tank calculator, I mixed 3g of Potassium Phosphate Monobasic to 100mL RODI water. I then dosed 2mL of that solution to my aquarium last night, which is about 180gal of water. This should bring me to 0.06 or about 20ppb, planning on some being absorbed by rock.

My test at lunch time today shows 81ppb!? That’s 0.25 for phosphate, which doesn’t jive (by my calculations) as per what was dosed. I’ll try again tonight with a different test, but makes me wonder what’s up with the Hanna (if anything)

Corals seem just fine, but wonder if anyone else has had this kind of issue?

 

[Semisonyx]

I ended up having a minute to do a second test. Now showing only 6ppb (0.018ppm), which is much more expected. Not sure why I got the first reading, the sample looked really clear, and I didn’t do anything different than normal.

 

[CNDReef]

That’s why a lot of people don’t trust the checkers. All it takes is a floater or a smudge and the reading can be off. I also use it and every once in a while I get a absurd reading and have to run the test again to make sure it’s right. Gets pricey though if it happens a lot.