I had to rush earlier, but let me expand some more.
My tank has residual levels of about .1N and .01P... you need ICP to detect the nitrate and Hannah ultra low will be between 1-3 ppb. Nothing suffers in my tanks. Nothing. People can find all kinds of things to complain about me, most if which are a bullseye, but not having thriving and growing stuff is not one of them.
I cringe when I see people post the parroted talk that people need to raise their N and P any time somebody has a problem. Could it help? Sure. Will it help? Who knows without more questions and stuff. It is not likely going to help unless they increase the availability - adding sodium nitrate and triphosphate will not likely do as much on the back end. ...so more import to start and more export if the import is overpowering the export.
There are also people who think that having higher N and P are what is moving the line forward, but this likely is not it either. The availability that keeps those levels high are what is doing the work - the man behind the curtain that goes unnoticed. These people would likely have much better results with lower residuals and the same availability - higher levels of N and P actually do slow down calcification and cellular processing even if they do not cause death and stuff still grows.
I also cringe when I see that posts that media or chemicals are the devil. They certainly can be, but it is almost always the application. They can work fast and you have to be smart, but when used correctly, they can be an appropriate tool, but that tool needs availability on the front end to help the corals while it works on the back end. Nearly nobody should be using any chemicals on a new(er) tank - there is just no need since residual levels are not set yet and the biological processes in the tank are still settling in.
I get it. Availability is hard to understand and hard to measure. There are test kits for N and P and people can latch on to numbers. This is why you have to pay attention and be smart. Heck, BRS has not even made a video about it - notice my disdain for reefers who get all of their knowledge from BRS videos? However, BRS does make a comment in their ZeoVit video that says something like "people think that this tank with it's low N and P is devoid of nutrients, but there are more nutrients run through this tank than any other that we have ever had." They are right about that, even though I hate calling N and P nutrients - soapbox here. (see, I do watch their videos before I roll my eyes at a lot of them)
The people who have always said "feed the fish more" are likely completely right. There are people who have fed their fish more and seen the residuals get too high, so the cut back on the feedings when they need to up the export.
My advice is to feed your fish so that they are actively growing. A tang should grow an inch, or more, a year. Then, match your export to the import so that your residual levels are low, but detectable... like 1N and .05P would be near my top to keep any type of coral at any time but 5N and .10P might not freak me out too much if I did not have a bunch of sensitive acropora. Keep your carbonate and calcium near NSW to match. If your N and P are rising, then don't cut back on feeding if you have lots of coral, but up the export. Using chemicals is OK as long as you are not going down near zero and you are going SLOW - natural methods using sandbed for nitrate and chaeto/fuge for nitrate/phosphate are better since they can never really get to zero, but sometimes this is not possible and media/chemicals are needed. DO NOT use chemicals and media unless you have a well-known, documented problem (like for a while) and you know exactly what you are doing. For example, if I took my fuge offline for a few months to clean or replace, my P would climb a bit and I would use some GFO, but it would be small and only enough to balance the import.
I have my method on my re-build thread, but I use multiple skimmers, sand and chaeto in a fuge to keep my N and P down. I also change water, but not for this. There are many ways to up export. Don't be scared of upping export and driving your N and P down, just make sure that you availability is higher.
Lastly, if people feel like dosing, then dosing commercial ammonium is likely better than dosing nitrate. At least the ammonium in available to the corals in a manner that they prefer. Some might cringe and see ammonium as a poison, and it is at high levels. However, so is nitrate and people do not even think twice about this. I just prefer to feed the fish and let them produce the ammonia/ammonium, but I guess that not everybody can do this.
