What is a full spectrum bulb? Sounds like a marketing ploy to me. No seriously I've heard of full spectrum bulbs but if marine keeping where only that simple. Most people use high intensity lighting at 10-12K for coral growth. When doing so you need to balance out the yellow light. The blue lighting will help bring back the washed out colors. Also full actinic NM420 can help certain algaes with their photosynthesis, without this your corals will starve and die. A "full spectrum" bulb is only good in fish only set ups to help bring out the colors in your fish.