Test results info everyone should read

[mark]

That's one of the reasons I got a pH monitor. For tests like CA, Mg a lot easier as your not trying to determine shades of colour, just pink to blue etc..

[Johnny Reefer]

If I'm not mistaken, most test kits instructions where a colour chart comparison is involved say to do it under diffused daylight.

[randallino]

Don’t test near actinic lighting for that reason.
Always shake the regents before using and rinse out the vials with tank water.
This is why I bought a Hanna PO2 photometer. Guessing which shade of blue is way too inaccurate. Seeing the real numbers was scary
RC

[GreenSpottedPuffer]

SOmething I never thought of before...good to keep in mind.