Hanna 713 Accuracy

[Virtual Balboa]

I recently bought a Hanna 713 phosphate tester and I'm questioning the accuracy of my test results. I've had a bag of Chemi-Pure Blue in my Aquaclear 70 for a couple of weeks. My average test results are around (.18). So I decided to try adding some BRS GFO along side the Chemi-Pure last night. When I tested the water again today I got the same reading. When I take a water sample I can always see particles floating in the water before I add the reagent. Would that skew the results? And is there a good way to filter the water I'm going to test to remove these particles? I also realized there are some very fine scratches on both of the cuvettes that came in the test kit. Because of this I try to load them in the same orientation in the tester when I take a sample reading and after adding the reagent. I question whether that's really helping as well. I've always handled the cuvettes with a micro fiber cloth during the testing process and clean them in distilled water after I'm finished. What do you think?

 

[Virtual Balboa]

That was a serious question. No one has experience with this?

 

[Crusinjimbo]

I believe the Hanna reads and intensity of light passed through the water and I doubt whether fine particles or minor scratches would have a detectable impact on accuracy. They are a +/- .04 tester. I have had visible sediment from the test reagent floating around in the vial with no impact on the measurement reading.

 

[hogfanreefer]

Is your GFO in a reactor? It may take longer than 18 hours to see a measurable change in your phosphate. Given the 0.04 range of accuracy it could be better and your testing noise doesn't show it. Test every day or two for a while, I bet it comes down.

 

[Virtual Balboa]

No, the GFO isn't in a reactor. Just a sock in the Aquaclear. I don't have a sump and adding a reactor seemed like I'd just end up with more things in the display than I wanted. The tank is in an apartment so I wanted the setup to be easy to maintain and less complicated. I did another test last night taking water from the filter area that doesn't have any obvious particles floating around. My phosphate results were down from .18 to .1 however I don't know if it's the GFO working or the fact that I didn't have a lot of junk floating in the water sample. I'm going to test it again in a few. I should add that I recently cured dry rock in the tank for a month then did a 100% water change as suggested by BRS. Afterwards my first phosphate test was .05 so I'm wondering if my rock and sand is leaching phosphates.