One thing I notice in doing my alk testing. I make sure the water is at the top of the measuring vessel.
In the above picture it is too low.
Here it is at the very top.
Also remember to be using the total marine al test
Use tank water to rinse three times then place cap on test chamber and press zero.
Then press read and stir the stick for 19 second and remove for the final second.
Placing cap on chamber when it is reading.
If I do the steps correctly it is repeatable for me.
In the above picture it is too low.
Here it is at the very top.
Also remember to be using the total marine al test
Use tank water to rinse three times then place cap on test chamber and press zero.
Then press read and stir the stick for 19 second and remove for the final second.
Placing cap on chamber when it is reading.
If I do the steps correctly it is repeatable for me.