I take it your talking about the hagen bulb. They are actinic (blue). They simulate deep water lighting. They are commonly used to compliment growing bulbs such as 10,000K.
I used to have my first small reef tank lit with two Life glo 2's and two marine glo's . The life glow 2's were 6,700K so the combination was great for a small tank with soft corals.
I can't say anything bad about them if thats what your asking. It will lite your tank up blue but wont grow much.
