Aquarium Lighting Tips

If hobbyists select the wrong type of lighting for a home aquarium, it can result in algae overgrowth, die-off of benthic plants, poor visibility and behavioral problems in fish. Fortunately, the challenge of lighting an aquarium is simple to address when the needs of the aquarium are taken into account. A proper lighting setup can make the difference between an unattractive, imbalanced aquarium and a beautifully aquascaped paradise.

  1. Evaluating Biotope

    • The most successful aquariums are not hodgepodge "community" tanks; they instead combine fish that require similar water parameters and tank setups. These natural-environment tanks (called biotope aquaria by enthusiasts) mimic the lighting and water chemistry of wild aquatic ecosystems. To select a proper lighting strength, aquarists should research the lighting needs of each resident fish species. Some popular fish, like zebra danios, thrive under very bright lights. Others--including most tetras and cichlids--become shy, sulky and dull-colored in the presence of bright lights. Lighting requirements should suit the biotope of every species in the tank.

    Selecting Kelvin Rating

    • Aquarium lighting fixtures are usually labeled with a Kelvin rating. This rating is a number--usually 5,500, 6,500, 10,000 or 20,000--followed by the letter K. Kelvin ratings indicates the wavelength or color spectrum provided by the lighting fixture. Shorter wavelengths, like 5,500 and 6,500, provide a reddish or yellowish cast, and longer wavelengths are blue-violet in color. Most aquatic plants can thrive under lights with shorter wavelengths, but reddish-toned plants and coral reefs require the ultraviolet rays found in 10,000 to 20,000 K fixtures. Additionally, tall tanks may need higher-Kelvin lighting because longer wavelengths are able to penetrate deeper water.

    Timing and Cycling

    • Most fish and aquatic plants need anywhere from 10 to 14 hours of lighting per day. Too much light can cause fish to develop behavioral problems and may encourage the growth of algae; too little lighting can cause plants to die off. It is critical to set up a regular and predictable lighting schedule. For very sensitive biotopes, it may be necessary to set up a timer. While fish from dark, tree-shaded environments do not require a "night light", fish native to open-water ecosystems can sometimes benefit from a whitish LED-based fixture that imitates moonlight. Breeders and professional aquarists may also adjust lighting times to mimic seasonal and lunar cycles; this can encourage temperamental fish to breed.