Given the wide ranges of KH
related issues and suspiciously high CO2 ppm
readings in some folk's tap water/tank water, this KH
reference method is a very useful thing.
The hardest thing is getting folks to actually make one and calibrate things.
So I did some digging and have a couple of useful links that make it clear.
Here is a good KH
Calculator using baking soda to make your KH
Note: make larger volumes(5 liters) and high concentrations, and then dilute.
This reduces errors(less is better).
So adding 5l of DI
H2O (1.321 gallons) and 4.992 grams of baking soda = 40KH.
Play around with the calculator, try 50 liters and 4 KH
, the higher volumes and higher the concentration, the less error you have, well up to a point[:p]
50 liters of DI
water and 40 KH
will give you 49.923 grams.
Now you have pretty high accuracy but you have a lot of KH
5 liters is not bad and you can toss the rest down the drain or trade to friends etc in the hobby.
Then you may take a 10ml sample of the 40KH reference and add it to a 90mls of DI
This will give you a reference of 4 KH
to within a very close tolernace depending on how careful you are weighing the baking soda, measuring the water volume and cooking the baking soda for 30-45 min at 400F before weighing to remove water and CO2
in the baking soda.
This should help you get going on making the KH
reference solutions and putting them to good use.
You may use the drop checker method, it's slow, cheap, simple, or you can DIY a DO membrane on the tip of a pH probe, and put the KH
ref solution inside instead of the dissolved O2
This is extremely accurate.
DO membrane material is fairly cheap per unit.