o.k.
lighting 101
V.H.O. = very high output flourecent tubes, they look very similar to the lighting you would use for freshwater, except they require a larger, high powered ballast to run the bulbs. v.h.o. is known for having the best color when it comes to actinic(the purple lights) bulbs.
p.c. = power compact flourecent tubes, not quite as nice quality as the v.h.o. but still has high output(compared to standard flourecent bulbs), typically the least expensive high powered lighting. the bulbs are smaller, there's two of them stuck together with a socket on one end. again you need a special high powered ballast to run the bulbs.
T5 = t5 connotates the diameter of the bulb, which is very small, they look like tiny regular output bulbs, but they have an similar output to v.h.o. , depending on brand. they too need a special high powered ballast. the color of the bulbs is better than p.c. but not as nice as v.h.o. has much higher output than p.c.'s.
Metal Halides = similar to the kind of bulbs that you see in a parking lot, very bright, the most like natural sunlight that technology has to offer. these bulbs require a taller canopy on the tank(12") because of the potential heat they create. they are a screw in bulb with a similar socket to a regular light bulb. of coarse they too require a high powered ballast to run the bulb, and typically some fans inside of the canopy to help dissapate the heat they create. the output of the bulb is higher than any of the other types of lighting and comes in 175, 250 and 400 watt bulbs. by far the best quality bulbs for growing coral. because the light emanates from such a small source it produces the shimmering effect you see in the ocean or swimming pool. probably the most asthetically pleasing of all the different types of lighting available.
a couple other things to familiarize yourself with would be:
"kelvin" = is basically the color of the bulb, the available spectrum is usually anywhere from 6,500k(yellowish color) to 20,000k(bluish color), with 10,000k(crisp white) in the middle. most people choose either 10,000k , 12,000k , 14,000k or 20,000k depending on what color you like and the types of coral you have. corals probably grow faster with a 6,500k to 10,000k bulb, but they produce more color when you use 12,000k to 20,000k(they make more pigment in their flesh to protect themselves from the increased u.v. in the bluer bulbs).
"ballasts" = generally, there are the older style magnetic, larger, hotter ballasts that will still run metal halide and v.h.o. bulbs, but people these days usually choose the smaller, more enegy efficient, electronic ballasts. they cost about twice as much up front, but cost about 25% less in power consumtion, and they give the bulbs about 33% longer life.
some people prefer the older style magnetic ballasts because you typically get a slight increase in output, but you pay for it with decreased lifespan.
well i hope this helps you some, imo, i'd say go with the metal halide, with actinic supplementation by v.h.o. p.c. or t5 is o.k. for actinic, but v.h.o. looks better
