I think that is sort of true, although, getting to 0 is probably tough. Most moderately shallow water reefs will average about .2ppm nitrate. We can't really resolve that with our test kits. The ocean though has lots of food, but our tanks don't. Some corals can take up N, and as mentioned in the linked thread, N is not really harmful. So, a surrogate, for lack of food, may be increased nutrients, such as N (and other untested nutrients and food sources that tend to go along with N). The problem then is algae can also take advantage of this and grow well too. Sort of the basic concept of coral biology is corals out compete algae, because during the day their symbiotic algae produces energy and at night, the coral can feed, providing energy. Whereas, for other algae, there is only energy production during the day, when the sun allows photosynthesis.
If we replace feeding with N though, some corals may have a tougher time regulating their zooxanthellae, as often corals seem to do so via nutrient regulation. I.e. when a coral eats something, it passes some food to the zoox, depending on how much it wants the zoox to grow. As ocean levels of N are typically quite low, many corals probably haven't developed capabilities to limit N diffusion from the water to zoox. N levels are just so low, it probably isn't really as necessary in nature and too much algae growth, or symbiotic algae growth can be a problem.
The reefers who keep non-photosynthetic corals have found it best to feed a lot and filter a lot, rather than to leave food in the tank, to possibly decay. This sort of mimics a reef best, there is a lot of food, but not much nutrients. This is difficult though and for photosynthetic corals, probably not as necessary, as we don't need as much food. So, letting N rise a bit as long as algae isn't an issue, seems perfectly fine to me anyways FWIW LOL.
