Hanna NO3 Dilution Questions

[Neil Cohen]

Using a Hanna HR NO3, got a blinking 75.0. Tried diluting 50/50 rodi and still got a blinking 75.0.

Tried 2ml tank water, 8ml rodi to get a reading. Came out to 41.2. So I multiplied it by 5 and can't see how that is correct. How can I have 212 ppm NO3 and still have anything alive? Have to be doing something wrong.

First thought was perhaps I reversed the dilution. That would give me around 50 but then the tester would have read it rather than blinking 75.0.

Any ideas? Heading to the LFS. Not loving the hanna. Grrrr

 

[Malcontent]

200 ppm nitrate is survivable. Salmon were kept at 443 mg/L for 8 months with no increase in mortality or decrease in growth rate.

 

[Gtinnel]

The only thing I can say is that your math seems correct. Well sorta 41.2x5 is 206 but at that high of a nitrate it doesn't matter.

 

[Neil Cohen]

Typo on the math, still a bit confounding. Have to dig out my old seifert and get a comparison since the ice storm doesn't want me to go to the LFS

 

[Neil Cohen]

200 ppm nitrate is survivable. Salmon were kept at 443 mg/L for 8 months with no increase in mortality or decrease in growth rate.

Interesting. Well, the tank is all softies and 8 fish (small except the tang and wrasse) and everything is growing.

 

[Randy Holmes-Farley]

Salinity impacts nitrate testing, so it is not a perfect method.

 

[Neil Cohen]

Salinity is about the only thing I am good at keeping stable...

 

[Dan_P]

Salinity is about the only thing I am good at keeping stable...

Randy was refering to the fact that when you lower the salinity of your sample by diluting it with freshwater, the nitrate value you obtain is higher than if you diluted it with saltwater.

 

[Neil Cohen]

I see. I should be diluting it with fresh saltwater vs RODI?

 

[Dan_P]

I see. I should be diluting it with fresh saltwater vs RODI?

Yes, dilute with fresh seawater, but please test the fresh seawater to ensure that it doesn’t contribute much to the nitrate test results.