It's a Coralife product and they make it in every type of bulb. From spiral pc, to t5 t8 t12. Not hqi though I don't think. Any store you deal localy with should be able to get it for you in the type and size you need.
BTW, with black gravel, you will never have that bright "spotlight" look. It sounds like you may need to replace your gravel and possibly lighting. T5 and Power Compact are your best options. Some eBay stores will even switch the bulbs for you at no cost if you purchase one of their lights. Tell them you want a 50/50 colormax/daylight bulb(s). For best results try to get at least 1w per gallon, preferably 1.5. Since your running 48" over 72, a 130w compact flouresent would work perfect. Also see if you can get a model with moonlight option. That is truely cool! These are on ebay, with moonlight, all day long for $100-125. Understand that by increasing your lighting like this, you invite algae, so make sure to stay on top of it. But another cool side-effect? You have enough light to grow most plants. There is no aquarium like a planted aquarium!!! Fish do better, aquarium looks more natural, clean less often, and natural oxygen for your fish. What more could you ask for?
