I have used all three over the years. I use LEDS and Halides now. I even have a small flouresent over anotehr portion of my sump. If you are clever, then for 300 bucks you can build a fixture that will burn up anything you could put in a 20 gallon long using LED components from rapid LED. With t5 you will have right out of the box "accreptable" intensity and decent color. Nothing matches the shear intensity and color you get from blasting your corals with Halides but the heat, logistics and costs make it more trouble than the extra cost and effort take. However Halides over a 20 would work well if you addressed the heat issues. I stll use a 250 watt halide over my 75 gallon portion of my sump and the animals in there love it. You wont loose with any of the three and if you do them right you can have success with all three. They all will work well. Lighting isnt that big of a deal actually. Any coral will color up under any lights if the intensity and more important WATER QUALITY is there.
