Stronger bulbs

[motoman]

Here's a question. I've got a 20 gal tank with a 18" bulb that is putting out 15 wts of 6500K. I'm getting into plants more and I'm going to need more light. My question is where can I get a bulb with the same dimensions and light spectrum but a higher wattage, say like 35 watts instead of just 15 watts? I checked Home Depot and they just hade the 15 watt bulbs in that size.  Is this possible or am I looking a building my own or buying a different tank hood that would hold two bulbs? I'd like to use the one that I have if possible. I seen some of these retro fit kits but I'm not sure if I can just gut mine and fit the kit in my old hood.

Motoman

[RedFish]

This is a very neat site with DIY lighting parts.  In Rochester NY, but they will ship.
Aquarium Hobbyist Supply
http://www.ahsupply.com/