What about inverts or amphibians?
Shrimp like RCS are fine.
I did mange to kill a few amano's, but..........was it due to solely to the KNO3?
I cannot say.
shrimp die for other reasons too, so that cannot be confirmed entirely, but the fish? Yes, they are survived without any issues. If some did die, then it would still not prove that KNO3 did it, only what did not do it.
There's a huge difference with the logic above.
Can you see and tell the difference?
Since you seem concerned about stress, what the heck do you think CO2 does to fish respiration????? How about low current and little surface turnover?????????
There's where you should be focusing in on. Ferts are essentially non toxic over a massive wide range of error for our purposes.
The most sensitive species are Salmon fry and trout fry, cold water hyper sensitive species adapted to ultra pure water, warm water species are far tougher. Look it up and read the fish that are suggesting this for. Poecilia reticulatus is the only warmer water tropical fish on the list there. Blue gill and catfish are tougher than nails. Trout/salmon are very wimpy wimpy.
The devil is in the details and methods & what specifically is being tested, are you comparing apples to oranges ................or something else?
Takes some effort and asking or more questions and how to apply them to our cases.
I bred shrimp, they tend to be much more sensitive to CO2 and nutrients, never had an issue even with inbred high grade CRS.
These where all culled from my planted tanks and make ideal models for toxicity testing.
This is the canary to compare ferts against. We can measure things like growth and brood production, sub lethal measures of stress and developmental stages.
Harder to do with fish.