Lighting requirements for a sump

Here's a good start -- I've heard of many people that had similar success using this lighting. I couldn't go this route myself, as I have very little space above my refugium and needed something more compact.

http://www.melevsreef.com/fuge_bulb.html

I'm sorry... I forgot you don't live in the U.S. Perhaps there is something similar in the U.K. I think the point is more how effective the general bulb style is (screw in compact fluorescent flood) and the color spectrum for good macro growth than the specific bulb itself. With our space limitations, I have 2 6700K T8 bulbs lighting our refugium and our macro does quite well.

I run our refugium on a 12 hour light cycle oppossite the main tank. I've had no problems with either macro (razor caulurpa and cheato) going sexual (a common reason for some people to run their refugium light 24/7). I run it oppossite to help stabilize the pH at night. It also is one less source of heat during the day.

Now I know why I forgot you're over in the U.K. -- you visit a local board here in the Carolinas. I've seen you on there, pretty much ignored your location line, and just figured you were somewhere near the Carolinas. LOL

Any photosynthetic organism benefits from a dark period. While our refugium is not currently in complete darkness during the day (I took the doors off of our stand to refinish them), the glass on all four sides is frequently covered in coralline (scraping the main tank is enough work most weeks), which blocks out the light pretty well.