"Coral" is too fine of a term. Some might "do fine" under 100-250 PAR, but some will not. It is best to identify which kind. I keep acropora and clams and they nearly all do better at 400-600, but some like to be in the 250 range. Yes, you can keep some alive with less, but just keeping them alive is not my goal - I want them to thrive. I have seen this kind of advice come from all kinds of places, but please do not trust it if it is from a light manufacturer - most of their "expert advice" serves themselves and not the hobby.
Then, there is the matter of survival vs. thriving. I keep a few Z&P in my tanks along with a few LPS every once in a while. They get a massive amount of PAR too. Light quality is also high. The zoas grow so fast that I have to kill them with kalk - this makes people mad because they are mostly collector strains, but I can turn a 5 polyp frag of Utter Chaos, for example, into 400-500 polyps in about nine months where you see a ring of new heads every few days. They grow like wildfire in high intensity light with good water quality. Do they need that much light? Doubtful. Can they be better with it? For sure.
Most of what we keep in our tanks is collected on one breath with a big hunk collected in knee or waist deep water. IR and UV can both penetrate well to 3-5 meters. There is no doubt that coral in the wild get it. Dana Riddle just posted a few charts about water penetration of light in different types (clarity) water - while the dude who he references has taken a lot of heat for his techniques and measurements, you can see the 1 meter values which probably give a rough estimation. When we were in the coral sea, the marine biologist there said that light from 350 to about 800 nm penetrates to 10 meters, but nobody in their area went below 3 to 5 meters to collect - they used snorkel and mask or waded in pools at low tide.
I don't have any comments about ramping. While it is not as natural, the 10 hours on/off on a light timer that is mostly dogma has yet to be beaten by ramping, so I just tend to subscribe to the "enough light for enough time" kind of theory. I have not really seen any evidence that one truly works better than another, so whatever makes the reefer happy is probably good here.
FWIW - 1 inch directly under my 20k Radiums is about 1700-1800 PAR. These are on 16" reflectors. This would be about 2000 on a 14" reflector and even more on a 12" or smaller reflector.
Why do people strive to "do fine?" These are living animals, so why would "do the best" not apply? Would any of us like to be captured by aliens and get care that is "just fine?" I think that most of us would like a high level of care, so I do not treat the corals with any less.
