They are inexpensive, but look at this forum discussion on it (I hope I can post this, if not sorry...)

It also has links to RC where there is a 22 page discussion on it. Has anyone tried them?

Thinking of ordering a 14k and/or 20k bulb to see how they look and whether there will be a little growth in my tank.

http://salt-city.org/showthread.php?t=15773