[Kolognekoral]

I would certainly agree, that reef aquariums are a fringe source of sales for LEDs, but this doesn't close out the possibility of specific types being produced in the near future. After all, we have many different T5 tubes available, which are designed specifically for various hobby lighting requirements. Yes, they are a bit expensive, but available.

At this point in time, I would think the fastest way to fill out the available spectrum would be with additional T5 lighting. This does have the immediate advantage of extending the blue range into the violet. The spectrum starting at 405nm is very inportant to corals.

While generally discussing spectrum, the article so kindly linked by jtma508 makes an assumption we may not need to make. It is dealing with the required, or better said utilized, spectra for zooxanthellae. The question for me is, just how important are the zooxanthellae for the well being of the coral? We now know that the corals are capable of covering their nutritional needs with considerably fewer zooxanthellae than most corals actually have. Indeed, corals will regulate their zooxanthellae populations via nutrient control, when in waters that are nutrient poor (< 0.01ppm PO4). In an aquarium, this low a level of nutrients is sought, but rarely maintained on a permanent basis. A reason why many aquarists have lightly browned corals. The corals are unable to control their internal nutrient level, as they would on a reef. In ULNS systems, such as zeolith/bacteria/carbon source systems, corals are clearly lighter in color and contain much lower densities of zooxanthellae. They are growing and otherwise healthy, which makes me wonder, just how important are the zooxanthellae? Clearly, they can be held a very low levels without stressing the corals.

This leads to the question, do we need to base our required lighting wavelengths on zooxanthellate needs or not? Is this why the red spectrum has not proved to be a problem with other lighting systems? Is this verging on infra red actually related to temperature reactions, as IR is actually noted as a heat source by the corals and perhaps the wavelength is not important, rather the heat it generates? As these higher wavelengths do not penetrate deeply into the water, perhaps it is the ambient heat of higher reef flats, warmed via the sun, that certain corals require, while others are perfectly happy at deeper than 10m with almost no red light and may even require these conditions. I am probably over simplifiing, but I suspect there is more going on here than directly meets the eye. We shouldn't assume that making the zooxanthellae happy means we are making our corals happy.