Do Hanna Checkers include everything you need to test?

[Peace River]

I got that suggestion here on R2R, it pains me I can't give due credit to whomever told me this
BUT,
The idea is your curvet will stay free of that cloudy residue if stored filled to the brim in RO. The water prevents the “chemical” from bonding to the glass

Whereas even if you clean them as described very often they eventually get cloudy somehow anyway

The calcium test is a universally agreed dud

Good feedback on the cuvettes. I bought a bunch of extra Hanna-equivalent cuvettes and change them out when they get cloudy or the line fades.