General Thoughts on LEDs vs other lighting

[heckeng]

I have been reading many LED lighting threads recently and also just got an AI Sol setup for my 90 to try out (coming from 2 x 250w Phoenix and 2 54w ATI T5) and I have come up with a couple observations and questions and I thought that the topic may be worth a thread of it's own.

First is dealing with the complaints about LEDs being dim in comparison to MH fixtures. I have a couple thoughts on this. Using my new Sols, it DOES appear that the lighting is much dimmer than with my MH fixture. I am only running 30% intensity on my LEDs though, so it isn't exactly a fair comparison. I wonder if the light spillage has much to do with the "perception" that the tank is dimmer. My whole living room is much dimmer now that I don't have 600w of MH/T5 light bouncing around. The LEDs are very directional and I get virtually no light spill now.

The second question has to do with the intensity of the LEDs and their burning corals. I am not the first to hit on this theory but I think it is worth some discussion. Part of the reason people think the LED tanks are dim is caused by the LEDs having to be turned down in intensity to keep them from burning corals. I think this is because of the high intensity of 450nm-470nm lighting supplied compared to MH and T5. The LEDs are so directional that they appear to be blasting the coral with those wavelengths. This is why the corals "Pop" so much more with LEDs than any other type of lighting.

I would like to hear from some of the people who have burned corals with LED lighting what colors the corals were that bleached. I would think that the more red the coral, the more blue light it absorbs, and therefor the higher the chance of cooking the zooxanthellae with any light system that puts out large amounts of blue/UV spectrum. Since Blue corals reflect blue light (that is why they are blue to our eyes) they would be burned more easily by the white LED and not necessarily by the Blue or Royal Blue LEDs as that light would be mostly reflected. If you compare fixtures and the ratios of white to blue LEDs, are they burning different corals? I suppose the fact that many of these units allow the user to adjust the amount of each spectrum may make this impossible to find out. As mentioned in several other threads, I think that the efficiency of the light to put out light wavelengths useable by the coral is what has the largest effect on the coral and causes the bleaching, not necessarily the light that appears the brightest to our eyes. With my other light system using a Maristar fixture with 2x 250W bulbs and Lumatek dimmable ballasts, I did have an instance of burning some Zoas by dimming the 250w bulbs to 175 watts each. This is counter-intuitive because you would think that it is putting out less light, so why would it burn the corals? By running MH lights at less "wattage" the color output by the bulbs shifts towards shorter wavelengths of light toward the blue spectrum. I wonder if the lights simply produced a new spectrum that the coral was much more able to use and therefor it burned the zooxanthellae? At the time, I ignored the issue and figured it was a water issue like my water had gotten cleaner and let more light hit the coral but looking back, I think the spectrum may be the issue that caused the burning.


If you have any other general question or thoughts on these lights, that is what I intended this thread for so share what you think!

And please, NO "how many light units do I need for a xxxxx gallon tank" questions.

Thanks

[FirstContact]

I have two led DIF pendants from Orphek. I like the Orphek pendants beause I could choose a 120 degree lens for that exact reason. Many manufacturers market the depth penetration of their products, but I am not going to own a tank deeper than 24". I wanted to spread the coverage. I also did not want to purchase more than one unit to cover my tank ($$$), and price point was a consideration. I purchased the DIF50-25K directly from the manufacturer and they sent me a DIF30-B for free. Pendants are my choice because I do not want anything between me and the tank. I was very happy to get rid of my T5 that stood on top of the tank. Even with the 120 degree lens, I burned a blue crocea clam under the DIF50-25K. I should have put it under the DIF30-B. I have since raised the height of both pendants. I would say that both myself and my corals are enjoying the benefits of LED lighting. This is my choice over any other product on the market since this is where I put my money.