The Lighting Requirements for Marine Aquariums

Saltwater aquariums are beautiful additions to any home, as they are capable of containing colorful marine life impossible to keep in freshwater aquariums. However, marine aquariums can be very difficult to maintain, especially if you are going with an aquarium that contains living coral. The lighting requirements for each type of marine aquarium, whether it be a fish-only, fish-only with live rock (FOWLR) or a reef aquarium vary tremendously.

  1. Fish-Only and FOWLR Aquariums

    • As their name suggests, fish-only aquariums only contain fish, with no invertebrates, live rock or corals. These types of aquariums are popular for those wanting simple, hardy fish like clown fish or damsel fish. Fish-only tanks typically do not need advanced lighting and will do fine with a stock fluorescent light strip like the kind that comes packaged in common aquarium hoods. Incandescent lighting, which uses two separate bulbs instead of a fluorescent strip, should not be used. Incandescent bulbs tend to heat the water, which could be problematic for saltwater fish that are sensitive to water temperature. FOWLR tanks also do not need fancy lighting and should be fine with a simple fluorescent lighting setup.

    Reef Tanks

    • Reef tanks, which are aquariums that contain corals and anemones, require very complex (and expensive) lighting. There are three types of fluorescent lights they will need depending on the size of the tank and the amount of coral and fish in the tank: high output, very high output or metal halide lamps. The type of light you use depends on the coral or anemone; some species require the use of very high output (VHO) or metal halide, while hardier species should be fine with the standard high output (HO) lighting. When determining how much lighting you'll need, a rule of thumb is to apply about 6 watts per gallon (for example, a 100-gallon aquarium would require a lamp with 600 watts). Because of the strong output of these lamps, an aquarium chiller may be needed to reduce the water temperature and counteract the high heat output of the lamps.

    Light Cycles

    • Simulating natural light cycles is important to not only reef aquariums but all fish tanks, in general. You may want to invest in a dimming switch to connect to your aquarium lights. With a dimming switch connected, you should turn your lights on about half power in the morning for about 30 minutes before setting them up to their max. In the evening, about 30 minutes before you turn the lights off completely, put the lights on half power. This simulates the rising and setting of the sun and allows the organisms inside to gradually adapt to the changing light. In all, fish-only aquariums should have about eight hours of full lighting a day and reef aquariums should have about 10 hours.

    Sunlight?

    • It's important that all marine aquariums (and tropical aquariums, for that matter) should be placed away from direct sunlight. A good place for marine aquariums is in a basement where very little sunlight can reach. This is because sunlight promotes the growth of nuisance algae, which can not only make your tank unattractive, but can choke the oxygen out of your water.