I wasn't thinking of fertilizer and CO2 when I set up the tank because I am rather new to having an aquarium. I had a 20 gallon and 10 gallon previously (and successfully!), but only one or two real plants, the rest were fake. So, when I set up the 55 gallon, it wasn't til after I decided real plants would be great AND the lighting fixture stopped working that I started doing some reading and realized that just a one bulb fluorescent fixture probably wasn't enough for a lot of plants and I might need to think about CO2 and fertilizer too.
SO, any advice about CO2 and fertilizer would be greatly appreciated as well!