Not at all sceptical and you’ll get no argument here. Seen more than a few find themselves in trouble attempting to remedy ‘problems’ using a range of products advertised as solutions.
Aside from managing chlorine/chloramine in tap water, time, good observation and ‘education’ is invariably the only friends you’ll ever need in setting up planted tanks. Even tap water with chlorine used to be aerated until it was gassed off. No one even has time for that anymore. Most folks used rain water to avoid even that hurdle 🤷🏻♂️
I'd guess that at some point some-one will produce a reliable test for fresh water, but until then a certain amount of caution is called for.
Duckweed index 😂
You could rebrand it frogbit index for fresh appeal Darrel.