If you're going to hang it from the ceiling or know a way to mount it above the tank.... the cheapest way is to go get one from Home Depot. They have the standard shop lights or designer ones ranging from $12-$40. Depends on your application and type of bulbs you intend to use. GL Robert.
homedepot is the way to go (since the thread is already half hijacked) for light fixtures.. if you go to a most of the not scarry homedepots carry bulbs made for plants that fit their cheap 48" fixtures..
only down side... silver diamond plate.. it looks retarded on almost every tank..