Lights?

[Rebel01]

Are the new T5 flouresents as good as metal halide for growing coral?

[Amphiprion]

Yes and no. There are certain metal halide bulbs and ballast combinations that would blow any T5 setup out of the water (especially some 250s, and most 400s--even one 175w bulb will outperform them). However, a good T5 setup will give you good results compared to the "average" metal halide bulb. This especially applies if they are overdriven with an icecap ballast. In a nutshell, if they are done right, you can keep practically anything (even with good color) under T5 fluorescents.

[Rebel01]

What do you mean by overdriven? I have a 55 gal tank. I was using a 250 watt metal halide mogul base that I had salvaged from work. I switched over to 2 54watt T5 bulbs in a GLO fixture that I got at B&B. I also have light stick with about 35 blue LEDs. The 250 MH messed up the color of my coral and I don't have a canopy to mount it in so it was just kinda hanging there real ugly. Should I build a canopy and reinstall the 250 MH along with the T5s or get a couple more T5s or am I fine like I am?

[Amphiprion]

I wasn't aware that you already had the 250w halide. Do you know what color it was? If it was one of the lesser kelvin bulb color temperatures, it tends to wash out the colors. Shoot for something in the 6500K to 20000K range (and be sure to only get bulbs rated for aquariums). As far as individual bulb choice and color, you may want to look on Reef Central for pictures of folks' tanks and the halides they use. I would just use the T5s for actinics, since the light level you were previously at was much higher than where you are now. Not even comparable. The GLO fixtures are only slightly better than compact fluorescents. You can't even compare them to a retrofit setup. In all, I would find a proper temperature MH bulb with a good reflector fixture (they look good, too), using your T5s exclusively as blue bulbs, and look into getting a vented canopy so that you can run fans efficiently through it. That way, you can also use a retrofit kit to mount your T5s and get the bulky, unnecessary fixture out of the way.

BTW, overdriven is when a bulb receives more input energy than it would normally require, thus making it run brighter, hotter, and shortening its lifespan by about 6 months (so closer to a year of needed replacement). Example, a 54w bulb will run at approx. 85w. with up to 50% more light.