Rand is a good starter reference book for folks interested in this field.
He discusses a lot of the basic tenents, which curiously are not acknowledge nor discussed by many naysayers in this hobby.

This will give you some good background about the topic and also how to approach the questions from a scientific approach rather than Preacher's stump speech and myth based hobby lore.

"Me too's" hop on board but that does mean excess NO3 is causing the issue.
Fish die for many reasons, many of which have absolutely nothing to do with NO3.
Findign a decent method to see why that might be vs a control is wise and obvious idea, one most naysayers seem to want to avoid but still speculate like they had a control

Do not fall for that baloney.
If you want to know more, then learn about the subject matter. You are often enlightened and sometimes if you are lucky, you will have a different view afterwards.

We all hold some prejudices, but that does not mean that these prejudices are right. Do not believe everything you think

Regards,
Tom Barr