Testing Alkalinity, specifically with Salifert Tests

five.five-six · Jan 9, 2018

Are you cleansing the sample syringe at the end of the test? My protocol is as fallows:

Draw as much sample water as syringe will hold and dispense to test vial

Shake and dump sample water.

Draw correct ammount of sample water and dispense to test vial

Preform test

Clean test vial and sample syringe with RO water

Put kit away.

I have had erroneous/extraneous test results but I usaly chalk it up me not counting drops incorrectly especially with calcium where I have to count to 8 which is more fingers than I have on one hand.

Mark Waltermire · Jan 10, 2018

I find whether I'm using Salifert, API, Red Sea or Hanna to measure alkalinity I will get numbers saying anywhere from 6.5-9.5DKH just depending on the test kit. Even Red Sea and Hanna will be up to .5DKH off for me and yes I do know how to use a test kit properly and am 18 so I don't think it's my eyes. Usually salifert will give me a number about 1DKH lower than hanna and Redsea. Hanna will always be in the middle of the 3 and I now will only use hanna because it provides consistent results every time and appears to be both accurate and precise for me.

Charterreefer · Jan 10, 2018

I just bought a Hanna DKH meter this week so I don't have to figure out what color I think the solution is and if I should add one more drop or not.

madweazl · Jan 11, 2018

Mark Waltermire said:
I find whether I'm using Salifert, API, Red Sea or Hanna to measure alkalinity I will get numbers saying anywhere from 6.5-9.5DKH just depending on the test kit. Even Red Sea and Hanna will be up to .5DKH off for me and yes I do know how to use a test kit properly and am 18 so I don't think it's my eyes. Usually salifert will give me a number about 1DKH lower than hanna and Redsea. Hanna will always be in the middle of the 3 and I now will only use hanna because it provides consistent results every time and appears to be both accurate and precise for me.

You had mentioned that you're seeing up to .5 dKh delta test to test using the Hanna; try using a syringe instead of eyeballing the water level in the cuvette. That made a pretty big difference in consistency for me and it's rare to see more than .1 dKh delta between tests now.

Mark Waltermire · Jan 11, 2018

madweazl said:
You had mentioned that you're seeing up to .5 dKh delta test to test using the Hanna; try using a syringe instead of eyeballing the water level in the cuvette. That made a pretty big difference in consistency for me and it's rare to see more than .1 dKh delta between tests now.

I probably wrote that confusing but I see a difference between Red Sea and Hanna. With Hanna I have their alkalinity test in ppm and when retesting I see consistency within 1-4ppm which is within the testing accuracy. I see the largest difference between API and all the other tests.

JTwinning · Feb 12, 2018

Where does everyone draw the sample water to test for the best accuracy? DT, sump before bag filters and treatment?

Randy Holmes-Farley · Feb 13, 2018

JTwinning said:
Where does everyone draw the sample water to test for the best accuracy? DT, sump before bag filters and treatment?

The location should not matter for parameters like alkalinity or calcium unless you are near an entry point for dosing.

It can never be wrong to get a sample from the display tank, if that is what you care about, but unless sump flow through is very low or you are actively dosing, they will be about the same everywhere.