I'd say it depends on what you are fragging, and you'll probably get several answers even then. I'm sure some of the members with frag tanks will chime in.
The best growth I've seen was under T-5 lighting, and the best color under 20k halides. I haven't had experience with LEDs yet, but I will be checking them out over the next couple months. I'll keep you posted! ...you keep fish?
I was thinking Halide lights myself. The LEDs I have already very good on some corals but pretty much all my LPS doesn't like them. Changed everything to LEDs and thought some was going to kick it before I could get them moved. On the fish No besides what are in my aquariums in my house.
If your question is about frag tanks only, which in my opinion are tanks where you place small frags on a temporary basis until they are healed and ready to be placed in a display tank, T5 lights will do a great job. If you are growing out frags to colony size then I have had the best luck with a combination of MH and VHO. Depending on size of tank, depth of water, and type of corals, the type bulbs and distance from the corals will vary greatly. The closer to 6500k the better growth and the closer to 20000k the better the color. Do your research as to the requirements for the particular frags you are going to have. In most cases people have only one frag tank and try to vary the bulbs to get the greatest chance for both growth and color no matter which type you go with (except MH then you only have one choice). Some choose a combination like MH/VHO or MH/T5. This is just my 2cents, but I have tried a lot of things.
I always preferred to mimmick the lights in your main tank. If you are using 14,000k metal halides by Reeflux then you should use the same over your frag tank. Does not necessarily need to be same wattage as most frag tanks are not as deep. I feel it creates less stress on the fragged coral after being cut, and then having to adjust to a new kelvin light supply while healing. That would go for whatever type of light you use T-5s, VHO, or LED. Once corals have healed and ready to sell, I also beleive their survival rate is higher in a customers tank. This in part to already being healed, and only having to adjust to the new lights. Most reef keepers who have corals and have been succesful already have good water parameters. So that is not as much of an issue to me. If you can afford it I would recommend going LED. Less heat and power consumption. When I get back into this great hobby I will be using LED fixtures over display and frag tank.
Good points Ralph about having the same lighting over display and frag system. That would make the healing process a lot easier.
