Alkalinity Testing Issues

[ocncheffy]

So I have multiple alkalinity test kits and there is a clear discrepancy between two sets, and I don't know which one to "believe" anymore. The Red Sea Pro and Aquaforest kit report a 7.8-8dkh, but the Hannah and Nyos kit test 9.3-9.4. There is a clear difference here, but maybe it's due to the testing methods. How should I go about resolving this issue? I've been following the lower numbers for awhile with success so I won't go changing things, but it is a bit concerning to know I could be closer to 10 on my tank...

Thanks,

 

[dank reefer]

I will say that no test kits are made equal and each test kit will give you different results. What you want to make sure that with which ever test kit you decide to use that they stay consistent.

I had come across the same issue when I was dialing in my CARX earlier on this year and I used Salifert, and Hanna ALK checkers and I got almost the same result as you did. 8.5-9 on Salifert 9.8-1.5 on Hanna. I was pretty surprised on the differences on both test, so I ran 3 consecutive test with both testing kits and the only one that was staying round the same was the salifert kit.

 

[taricha]

Consistency matters more than accuracy, but if you really want to know you can do a known alkalinity standard...
Randy's DIY Alkalinity standard

 

[PatW]

I use Red Sea Pro, Salifert and Hanna. My DKH comes in at about 8.0 for Hanna and Red Sea Pro. Salifert comes in about 8.7. But tests accuracy is only approximate and for these tests, that is not bad. What is important in alkalinity is the trend. You want stability and if it changes whether it is rising or falling. When I test multiple days with all three tests, they can diverge in different directions but all within their error range. The Hanna is the most precise (reproducible) usually plus or minus 0.1 DKH. Red Sea Pro is plus or minus 0.2 DKH and Salifert is plus or minus 0.3 DKH.