Thanks, I found the EI description on The Barr Report and will do some reading. Appreciate it.
Shrimp make excellent models for aquarium toxicity in Freshwater systems. Since they breed like flies, and we often cull out the weaker color forms, we have ample test subjects.
They are like the canary in the coal mine.
So a biological assay test, the shrimp become the "test kit" and the plants, algae etc.
I'd rather folks spend time on on the goal; nice fish/shrimp and nice plants, rather than the testing methods. Who got into this hobby ot measure pH and NO3? I've not met anyone yet.
They have uses to be certain.
But often(more than not), folks end up with inconclusive results, or results that cannot be correct due to test errors, no standards to compare to.
It's ironic because I have a lot of experience with testing and methods.
But often the advice based on what the goals are for hobbyists, goes towards not using the test kits. A good old water change is often much more benefit.
If you use the graphing modeling calculator(based on infinite series dilutions), you can still get plenty of Science and predictable outcomes. You target a range, not a specific ppm. In reality, plants, fish are able to do quite well in a variable environment and even if you test and dose carefully, there will still be a lot error associated with that.
In other words, you gain little in spending the time testing a great deal.
Most test a little while, then perhaps only when something is wrong, and not much otherwise. So most of aquarium management is Social/human, not Science issues.