Fish tanks are often as much for aesthetic pleasure as they are a place to keep your pets. This is why many people choose to add aquatic plants, aquarium decorations and keep tropical fish. However, like any piece of art, the fish tank is not complete without lighting and the light needs to serve two purposes.
First, aquarium lighting needs to mimic daylight, as much as possible. This helps the fish regulate their daily cycles and serves to let them know night from day. That means 12 hours of light is necessary. This type of lighting can be achieved with a bulb or two in the hood that goes over the tank.
The second purpose of aquarium lighting is for night use. Since you will likely want to check out your tropical fish after dark, some carefully placed lights can be helpful. These may come in the form of aquarium decorations that serve as miniature spotlights or smaller lights in the lid. The idea here is to highlight the tank without making it too bright for the fish which will tend to get confused. Lunar lights are ideal for night use, since they illuminate enough to view nocturnal behavior, but don't disturb anything.
The type of light you select will depend on the type of aquarium you have. Deep reef tanks, for example, will need more blue light, called actinic lighting. This is usually combined with daylight bulbs for easier viewing of the tank. Remember that some fish and aquatic creatures do not fare well under direct light, so they should be given plenty of shade to hide in if necessary.
Choose lights that are cool so they don't overheat the fish tank, which can be dangerous for your pets. The daylight lighting should include daylight spectrum ranges which stimulates growth in plants. You can find these at your local pet shop. Lighting will make all the difference in how well your tank does.