Since this is a low tech forum I assume you want a low light tank, which is what a low tech tank generally is. A single T8/T12 bulb will not give enough light on a 55 gallon tank to grow much of anything except mosses. A two bulb light of that type will be low light, but close to the minimum. A FishNeedIt 2 bulb T5HO light will give good low light, enough for all low light plants. A Catalina 2 bulb T5HO light, with the bulbs spread apart about 6 or more inches, perhaps this one http://www.catalinaaquarium.com/stor...oducts_id=1842
suspended about 6-8 inches above the top of the tank, should give you low medium light.