After struggling with pale colors I've run the gauntlet of things to help. Increased feeding (which caused algae blooms), select KZ suppliments, AF method and suppliments incluing all mico/macro elements.
Being at a loss I tried Kn03 dosing. The first time I did it I got RTN. I'm guessing I dosed too much, but didn't know that at the time. I went back to trying other methods and throwing tons of money at my tank trying to figure out what I was missing.
Feeding fish more didn't work I moved on to feeding reef roids & reef chili thinking a more targeted approach would help. I did see increased PE but colors were still pale (red planet was light pink planet).
After several trips to WWC and knowing they run N03 in the 30+ range I wanted to try N03 dosing again. So about 6 weeks ago I bought a small bag of NaN03 and dosed a small pinch once a week. I should also mention in the past I've struggled with algae, P04 that goes up over time and I have little to no coraline even on my tank that's been in continuious operation for almost 10 years
After dosing for a few weeks I saw my P04 go down a little and algae decrease some but not much color improvement. My N03 stayed at 0 so about two weeks ago I started dosing N03 daily. The same small pinch of N03 but daily instead of weekly
Since then, my red planet has gone to a blood red with a deep green base, my other corals are definately showing coloration improvement and for the first time I'm seeing large patches of coraline algae that I've never had before. I'd get them in the past but they would be fairly small and usually die off after some time and chip away
The other observation that's odd, is my fish will at times knock a small branch of SPS off that hits the bottom of my BB tank, in the past it would quickly bleach/ die in a couple days and I'd siphon at some point when cleaning detritus.
Since my N03 dosing I've been watching a branch that's being blown around my tank for the last 10 days or so and not only has it not died, but the base of the branch encrusted and it is now growing a polyp where there used to be skeleton.
I think it's important to say I have by no means scientifically proved that N03 is my ultimate solution, and it is 100% not a solution for everyone. However, if you're struggling with pale corals it is one item that should be looked at and potentially tried.
It's also my guess that this is a more common issue for tanks with a fuge, bio pellets or carbon dosing of other sorts and/or tanks with light bio loads(all of which I have).
I've read the "feed more" suggestions and have tried that with predictably higher P04 and algae to follow.
I remember the hobby a dozen or more years ago trying to get enough light and remove enough nutrients. It's interesting to see threads about cooking corals and starving them as technology has increased.
Some of the old school reefers find guys dosing N03 nuts, as we're stripping our tanks to just put it back in. But I kinda like the idea of it, much like using an RO/DI to strip all the calcium and other materials from tap water to just put them back in with the salt, but it's being put in at known ideal values