The KH reference solution will be made available commericially here shortly.
They are highly lab verified accurate and only requires the drop checker and pH solution.

So you add the KH solution, then the pH indicator, invert and add to the tank.
It's small and you can glance and make sure there's enough CO2.

I can do this with plants and also know when the CO2 issue might have occured through time
Not everyone can.

But even that, a drop checker is still useful to me or others.
I'll finally get to the pH probe/ref solution method coming up in a week or so.


Regards,
Tom Barr