API Alkalinity Test Kit, doubling volume for improved percision?

Exus · Feb 28, 2023

So, I like to use the API Alkalinity test kit because it just uses the one dropper, but I miss out on the accuracy of the Hanna Checker or other multi-step test kits. The API test is 5ml tank water and each drop of the reagent is +1dkh until color changes. So I thought, what if I just double the volume, wouldn't that improve the accuracy? With 10ml tank water, wouldn't each drop be +0.5dkh until color change. Is my reasoning sound or would this not work like I expect?

exnisstech · Feb 28, 2023

I don't know but it sounds like it should work unless the kit just doesn't have the ability to display anything more accurate than 1dkh. Maybe do 2 tests, one with 5ml and one with 10 and compare the results

I get that it's easy to use but if it doesn't read anything more accurate than 1.0 dkh I don't think it's accurate enough for anything more than a random check really. You couldn't even use it calculate consumption rate of alk.

Randy Holmes-Farley · Feb 28, 2023

Exus said:
So, I like to use the API Alkalinity test kit because it just uses the one dropper, but I miss out on the accuracy of the Hanna Checker or other multi-step test kits. The API test is 5ml tank water and each drop of the reagent is +1dkh until color changes. So I thought, what if I just double the volume, wouldn't that improve the accuracy? With 10ml tank water, wouldn't each drop be +0.5dkh until color change. Is my reasoning sound or would this not work like I expect?

It does not improve accuracy, but may improve precision. The limitations to doubling the volume in any alk titration test is the ability to accurately measure the initial liquid volume and the volume of titrant added, and to see the color change properly.

I show how to do a DIY alk test on hundreds of ml of tank water here:

A DIY Alkalinity Test: By Randy Holmes-Farley - REEFEDITION

Alkalinity is one of the most important measurements that a reef aquarist can make. It can become rapidly depleted in many aquaria, requiring frequent measurement in order to maintain stable levels.

www.reefedition.com