Most marine orgainisms are taken from depths of meters, very often 10 meters or more. Not a matter of feet. There are not a lot of people keeping lagoonal specimens that actually come from shallow waters. In the marine trade 10 meters is considered shallow. Specimens for reef tanks come from 10 meters to 30 meters depths. Besides, look at graphs and charts and see how little light but blue penetrates beyond just a few meters.
I fail to see why you even wish to discuss very deep water fish when the discussuion is about corals fish tanks. Alaskan fish as do most fish only come near the surface for food. Very few fish actually chose to be siloeted by the sun as it makes them easy prey, or targets. Alaskan corals are deep water corals, very deep, there is barely even any blue light at their depths, they do not have algae living in their tissues. Nearly all fish in Alaska are dep water fish. THe nets, sringer lines and traps are not set or used in shallow awaters. Unless swimmers using mixed gases swimming down for them (fish or corals) they are typically only seen when deep sea trawlers bring them up in their traps/nets. Alaskan fishermen who sport fish use bvery large reals with extreme amounts of line on them. Alaskan corals are not dependant on sunlight as the are chiefly filter feeders and also utilize dissolved organics. Deep water fish and corals over a long period of evolution have adapted to a near absence of light, every where not just in Alaska.
Most coral fish (definitely not corals) never venture more than a few meters out of their territorries in their whole life spans. They do not swim through out the ocean and have not through evolution adapted to any changes in lighting etc. As do open ocean fish and zonal fish, from very deep depths.
If lighting was/is not an important issue with corals then there would be no multitude of tests on different bulbs and different lighting PAR, PUR and intensities. Periods of drakness is generally considered a common known fact that is beyond argument.
Skinner, a well known, actually famous man, in the field of mental health used to lock his own children in a closet without food and light and they had to perform different acts to get attention, food or to go to the bathroom. Some people would say that is OK, some people would say stressful at the least.
Any one can obviously do as they wish with their reef tanks, as unfortunitly there are not yet any licensing requirements involved in keeping them.
I am just repeating that knowledge that has come through study, work and research, not casual untested observation. Higher form invertebrates that are dependant on lighting need controlled moon lighting or complete darkness for optimum health and growth. The difference between optimal and good health and growth is obviously pretty hard to put numbers on. Quality reef keeping usually means making many efforts to try to mimic nature because that is what the organisms have evolved into seeing as best. Doing what ever we want for viewing enjoyment is usually not considered making efforts to mimic nature.