Let's talk about bio load.

[Aquattro]

Originally Posted by Samw

Why is dissolved oxygen impossible to measure? There are dissolved oxygen meters. I have one.

Meters are rare items owned by hobbyists. And titration kits don't work well at all.
Not impossible, but not something that is useful, therefore difficult to justify a meter.
Hobbyist meters are also likely not maintained well, so the value could be way off.