I've recently gotten into the aquarium hobby. I started off by buying a 30 gallon tank & stand w/ everything including 3 fish off of craigslist for $40. I then decided that it would be fun to have some real plants with the fish but later found out that you need much more light than what you would normally get with those standard perfecto light hoods. After checking out how expensive the more powerful lights were I figured it would cheaper and cooler to make your own supped up light hood.
I used those spiral compact flourescent bulbs you get at the Home Depot. I got a 4 pack of the n:Vision daylight 14 watt bulbs for about $10 since they fit nicely in the original perfecto brand hood. The "daylight" variety is important because plants only absorb certain spectrums (ie colors) of light found at both the low (reddish) and high (blueish) end of the spectrum. The "daylight"'s include more of the blue spectrum which is especially good since that part of the spectrum can penetrate deeper into the water to the plants at the bottom of the tank.
The light sockets were $1.50 a piece and made of porcelain (which I found can easily break if dropped). These didn't come with any bracket to enable you to mount the socket to anything, so I had to fabricate some out of aluminum angle iron. The brackets were mounted to an inch and a half wide piece of steel bar stock. I drilled the bar stock in precisely the same locations as the plastic standoffs on the original plastic hood. This allowed me to secure the bar to the hood while leaving a gap for wiring between the bar stock and the hood. The bar stock was also drilled with larger holes to allow the wires from the socket to be routed through. I used rubber grommets in those holes to prevent the wires from getting rubbed against the hole edges. I removed the original switch and wired everything in parallel using water resistant twist ties. I also painted the interior of the hood with flat white paint which should reflect more of the light back down into the tank and reduce the heat.
Note: to drill bar stock and brackets I had to use a drill press and some cutting oil to keep the bits from wearing out prematurely.
Since the lights did produce a lot of heat, I drilled several holes in the plastic hood for ventilation. That still wasn't good enough so I added a 12 volt PC fan, by using a AC-DC transformer from radio shack (one of those wall warts) and wired it to a 5 watt 100 Ohm rheostat that I got from Jamesco (a local electronic supplier). To make it nice, I mounted a female DC socket in the middle and wired everything to it. The rheostat (at the bottom) lets me control the speed of the fan (by varying the resistance) so that it doesn't get too loud. The fan is mounted on the top and I used some rubber plumbing washers as standoffs to minimize the vibrations transmitted to the hood.
I also added a moonlight, by attaching a blue cold cathode light kit used by PC-modders. Since they run off of 12 volts, I just wired it in parallel to the DC fan (excluding the rheostat). The light and fan stays on even when the main lights are off. They provide a soft light that some believe mimic the light coming from the moon which might encourage the fish to breed.
Overall I estimate that I spent about $70 for this project. The largest cost was the AC-DC transformer at $26 and the cold cathode light kit at $10. If you take those out the cost is around $35. This gives me 56 watts of power (just under the 2 watts/gal target that I wanted). The best part is when the bulbs wear out, it only costs about $10 to replace all of them.