A few details about your fixture might be helpful here... If a standard fixture though your kinda stuck since it has only the ballast for the T8 supported, and retrofitting it will cost more than a simple upgrade to a different bulb type.
Check this out retrofitting: http://www.instructables.com/id/CFL-Bulb-The-Cheap-Upgrade-to-the-Aquarium-Hood-L/
or
http://www.aquariacentral.com/forum...ompact-Fluorescent-(CFL)-Strip-Light-Retrofit
or
http://www.aquariumforum.com/f34/diy-cfl-lights-original-fixtures-26379.html
I use this myself(pick the lower watts for new tank then upgrade when things are ready later on with higher watts): http://www.plantedtank.net/forums/showthread.php?t=153195
This should get you started.
Imi
Check this out retrofitting: http://www.instructables.com/id/CFL-Bulb-The-Cheap-Upgrade-to-the-Aquarium-Hood-L/
or
http://www.aquariacentral.com/forum...ompact-Fluorescent-(CFL)-Strip-Light-Retrofit
or
http://www.aquariumforum.com/f34/diy-cfl-lights-original-fixtures-26379.html
I use this myself(pick the lower watts for new tank then upgrade when things are ready later on with higher watts): http://www.plantedtank.net/forums/showthread.php?t=153195
This should get you started.
Imi