The setup:
My first attempt was a wooden frame that sits over the top of a sump (which is located in our loft/attic, with water pumped up through the walls/ceiling via a peristaltic pump).
It was lined with thin clear plastic to protect the wood, with 4 outdoor, waterproof bulkheads holding a 15w spiral compact fluroescent bulb in each. The bulkheads with the bulbs in are mounted on top of the plastic, about 1" away from the mesh on each side.
The 1200lph pump pumps water up to the PVC pipe with the plastic mesh (9" wide, 18" long).

The problems:
The normal household 15W spiral compact fluroescent bulbs are:[list]
a) too dull
b) too bulky to make a nice compact filter
c) too low colour temperature[/list]
I'm having a lot of problems trying to get the mesh to not splash water, I've had two attempts at cutting the PVC pipe, the second attempt worked better, but cutting with a dremel seems to melt the plastic behind the cutting wheel and end up with a slightly wonky cut. The other issue is that when cut, the PVC pipe seems to push the center of the line that's cut together and almost look like you've not cut it at all, or that it's being compressed, like a spring almost, probably the way the plastic is made.

Some new ideas:
Well, I've started a new design.
The lights:
I've got 4 Philips PL-L fitting, 18W 6500K bulbs, with ballasts that control two bulbs each.
The "pros":[list]a) For only 18W, they are amazingly bright
b) they are a "cool daylight" 6500k colour temp, likely to grow algae a lot better
c) much more compact, about 1/3 of the depth of the spiral/energy saving bulbs[/list]Cons:[list]a) Require a seperate ballast
b) Cost very little (around 3.50/$6 per bulb), however the ballasts cost a fair bit (16/$27) each[/list]
The new design I'm working on, will have a similar wooden frame, with plastic inside, but have the lights behind the plastic, with mirrors behind them to double the output of the lights, this will make the width of the filter much much smaller as the plastic on the inside of the frame can be 1" away from the frame from either side, and only need to be 1" wide on either side of that to contain the lights and mirrors.
I'll post some photos as I get along with it this weekend.