The biggest longest running mistake is mass vs atomic ratios.
Redfield ratio is 16:1 for N:P, this is atomic.
It's off by a factor of 2.2 or so if you convert to mass.
Add the NO3: PO4 and you add even more issues.
Generally, I've not found any examples of long term uptake that exceeds more than 3-4 ppm per 24 hours of NO3.
For NH4, this is about 0.8 ppm per 24 hours.
Virtually every single aquarium will use LESS than this.
This goal is not to dose exactly some specific ppm, the goal is simple: provide nutrients, so that nothing is even in short supply.
This range is roughly 10-30ppm, I tend to keep my tanks in the 10-20ppm range for NO3. PO4, this is less important, but seems to get a free pass these days(that was hardly the case 10-20 years ago), but anything from say 0.4ppm to 5 ppm seems widely used.
Uptake here can vary widely depending on dosing frequency. I dose 4-5ppm 2x a week. I use to dose 1 ppm once a week, some dosed 0.2 ppm 2-3x a week, others dose daily 0.1ppm etc.
I have folks asking me why their ADA tanks are filled with algae, or why the Seachem stuff causes algae or their plants are not growing either. 9 times out 10, it has little to do with the N vs NO3. Sure, we correct them and get them back down, but it will not save them from the original issues that they have, too much light, not enough current/CO2 etc. Those 2 issues have not changed since I've been on the internet, so 18 years now.
If they have 60-100 ppm of NO3, well, then they likely have other issues and are not doing the water changes etc. The target is 10-30ppm, most folks should EASILY be able to hit that. PO4? I do not know, maybe 2-5ppm. I do not see much difference.
CO2? light? Massive differences.
We have dosing calculators with both raw chemicals and brand name products, so the folks can use those if they are aware of them. Plug and chug.