ReefWreak,
I used my Rebel XT, 100mm macro, tripod, and remote shutter release. I think that shot was an 8 second exposure. It was taken during the night, and every light in the house was turned off except for the VHO actinics over the tank.
I had to do a little color correction in post-processing with photoshop. The camera's attempt at white balance turned the purple tips to a drab blue, so I had to pull some blue out and add pink to get the purple color right.
The coral is actually a GARF purple bonsai. The body of the coral doesn't show any of that greenish hue under daytime lighting, it's more of a light/tan color. The polyps are always bright green. It's still a nice looking coral during the daytime, but it's absolutely stunning under actinics.