They did die(amano shrimp) at 120-160ppm NO3++ levels.
I'd rather folks say: shrimp do not like high NH4, that's where most of the toxicity issues arise. Few have ever added specifically NO3 from an inorganic salt to verify the direct NO3 impact, they just measure the left over fish food/waste etc that starts off as what? Organic Nitrogen, then processed by fish using O2, then organic N again, then bacteria munch and oxidize more till we get NH4..........now we have another group of bacteria that munch of NH4=> NO2 then another bacterial set NO2=> NO3.
That's a bit different than saying inorganic NO3 from KNO3.
I can kill fish with zero ppm of NO3 with that method.....
But folks want to make statements about NO3 in general and then apply them to KNO3 dosing.
That's very dangerous and may support myths without testing and verifying if they are right or not.
So you add KNO3 and see.
I did.
Then you go back and try to add 120ppm of NO3 via that other pathway
Lots of death there, never made it to NO3, all the shrimp died before the nitrogen was made into NO3...........
Regards,
Tom Barr