Should I Turn My Fish Aquarium Light Off at Night?

Before determining how much light to give your fish each day, check the care requirements for your individual species, as needs vary slightly. However, most fish require around 12 hours of light a day. Fish such as goldfish will lose their color without light, and some fish may stop eating, become lethargic or become ill without sufficient lighting.

The most common problem caused by excessive light is algae overgrowth. When a tank is lit 24 hours a day, algae can grow much more quickly. This can make your tank look dirty and if you have natural plants, algae may out-compete them. Some fish need periods of darkness to sleep, and without sleep may become lethargic or stop eating. Many fish species are stressed by excessive light and may begin fighting with one another.

Light timers are the easiest, most effective way to regulate your fish's night/day cycle. Simply set the timer to turn the light off at the same time each evening and to turn it back on the next day. If you don't want to use light timers, set an alarm and turn the lights on and off at the same time each day. Consistent light cycles that replicate daylight and nighttime reduce stress and mimic natural environments.

If you use a heat light to warm your aquarium, you may need to use an aquarium heater instead, particularly if you have tropical fish who require warm temperatures. Ceramic bulbs that produce only heat without producing light are also available at many pet stores, and are excellent alternatives to bright heat lights.