Live Rock Lighting Requirements

Live rock is a special form of rock used in saltwater aquariums. The rock is porous and contains dozens of multiplying copepods, small, shrimp-like animals that inhabit the numerous pores in the rock. Copepods provide food for a variety of saltwater fish, such as gobies and butterfly fish, and crustaceans such as reef shrimp. As with with most saltwater setups, aquariums containing live rock require special lighting conditions essential for maintaining a healthy environment, but note that live rock lighting is not strict, and its basic requirements are flexible.

  1. Fluorescent Bulbs

    • Typically in the aquarium market two types of lighting are available: incandescent and fluorescent. Incandescent lighting uses two bulbs with coils similar to standard household light bulbs. Fluorescent bulbs, however, use a long tube with illuminated gas. Fluorescent bulbs should typically be used with live rock, as the bluish hue they provide simulates more natural lighting, prompting creatures within the rock to breed and emerge during the day, where they can be consumed. Fluorescent bulbs also do not heat the water as much as an incandescent bulb may, making temperature regulation, which is essential to the health of live rock, more manageable.

    Timing

    • The lights over live rock should be on at least 12 hours a day. For proper growth of the organisms in the live rock, as well as simulating the natural light cycles they're used to experiencing, the lights should be on 12 hours a day. This will most likely result in algae, which grows in direct correlation with the amount of light an aquarium receives, but they are a necessary nuisance and can be controlled via algae-eating fish or by daily cleaning.

    Size and Intensity

    • The intensity of the fluorescent light is often measured in Kelvin, or "k" for short, and is typically labeled on the bulb's packaging. Look for at least a 10,000k light strip, as anything more than that may kill off the organisms in the rock. When selecting lighting for live rock, make sure the light strip stretches over the entire length of the tank. The wattage selected usually depends on the size of the tank and should usually be about 4 watts per gallon of water. As an example, a 55-gallon tank with live rock should have a 10,000k, 220-watt fluorescent light strip about 48 inches long.