I would like to keep the watts as low as I can seeing as it runs 18hrs a day.
Filtering is proportional to the wattage. So half the wattage is half the filtering. Also, higher wattage for less hours is better than less wattage for more hours, even though the same power is used. This is because algae grows fastest (and absorbs nutrients the quickest) with strong light.
If you're making out of plexi you could get the plexi with the mirrors built into one side
Having used mirror plexi, I found that the mirror peeled off after exposure to salt. Took about a year.
flood lights with the curly bulbs inside. These work really well because they have a reflector built into them and they are encased in glass so the spray can't get on the curly bulb itself.
Although floodlights are easier to clean than curly-Q spirals, floodlights concentrate the light too much in one spot. Spirals in big reflectors grow algae the best.
If I really like it and want more light power I might end up building a different one with leds on the out side, so that I can keep my watts down.
Unfortunately you can't save on wattage. Whether it's CFL, T5 or LED, you still need the same wattage. Less wattage is less filtering. And LED's are for experimenting only... not results (you won't get any results).
Is there +'s to having more than recommended? Meaning if I have 100 gal do I get twice the benefit of a 20 inch screen versus 10 inch or do the benefits of overdoing fall off at some point?