Lighting is one of the most important elements of both fresh water and salt water fish tanks. Adequate lighting is necessary both for the health of the fish and for the health of the plants. In addition, lighting increases the aesthetic appeal of the aquarium by transforming it into a focal point for any room. Although there are a variety of lighting options for a fish tank, replacing a light bulb is done in the same basic way.
Turn off the fish tank light and unplug the cord form the electrical socket.
Place one hand on either side of the light ballast, which sits on top of the fish tank, and lift it off of the tank.
Turn the light upside down and place it on a flat work surface such a table or the floor.
Remove the existing light from the light fixture. If you have a standard incandescent light, compact fluorescent light, LED or metal halide, simply grasp the bulb in your hand and turn it counterclockwise to remove it. If you have a fluorescent tube light, grasp both ends of the light bulb tube with your hands and pull the bulb away from the fixture.
Discard the used bulb.
Insert a new bulb into the light ballast by reversing the steps taken to remove the old one.
Pick up the light fixture and turn it over so that the light bulb faces downward. Place the light fixture back on top of the aquarium.
Plug the light's electrical cord back into the wall and turn the light on.