Heating and Lighting

In their natural reef environment, marine fish will experience amazingly stable water parameters, including water temperature. The ideal temperature range for most marine fish found in coral reefs is between 72° and 79°F. In a home aquarium, a temperature somewhere within that range should be established and kept as consistent as possible. A combination of the correct heating and lighting equipment will create the optimum environment for your fish.


Marine aquariums should be equipped with a thermostatically controlled heater. A heater ensures that the temperature is maintained within the acceptable range. Heaters are available for all sizes of aquariums, but you must ensure that the heater is correct for use in saltwater and that it has ample wattage to heat the aquarium water.

Aquarium heaters are fairly inexpensive and will do the job quite well. Submersible heaters contain a heating element and a thermostat in a small glass tube that can be attached to the wall of the tank with suction cups or hidden among the rockwork in the tank. There are also heaters available that clamp to the top of the aquarium, putting a glass tube into the aquarium and leaving the temperature adjustment dial above the surface. No matter which kind of heater you choose, make sure the temperature settings are easy to read, it can be easily adjusted while still in the aquarium, and it is fairly sturdy and not easily damaged.

When purchasing a heater for your aquarium, you will need to decide how much wattage it will have. Simply put, the higher the wattage of a heater, the faster it will be able to raise the temperature of the aquarium water. You will want the heater to have approximately 5 watts for every gallon of water in your tank (or 3 watts per gallon for a large tank). For example, a 75-gallon tank will require a heater of 250 watts. This wattage can come from one heater or a combination of two heaters.


The lighting you choose for your saltwater tank will depend on whether your tank will contain only fish or be a mini-reef tank. Fish-only tanks require no special lighting other than that which will allow for the most optimal viewing of these beautiful creatures. A standard pair of normal output fluorescent lamps should do the trick, with the amount of wattage to be determined by the size of the tank.

Lighting plays a very important and complex role in a mini-reef aquarium. Many marine organisms generally included in such a setup would not survive without lighting of the proper intensity and spectrum, so you will need to provide artificial lighting that imitates natural lighting as closely as possible. As with heating, you will want your lighting system to produce a minimum of 3 to 5 watts per gallon of water.

Fluorescent fixtures and metal halide lamps are light sources commonly used in mini-reef aquariums. Fluorescent lighting is usually more convenient, less expensive to purchase and to operate, and outputs less heat while running. On the other hand, fluorescent tubes can really only be used in shallow tanks (20 inches high or less) because they don’t penetrate the water very deeply.

Metal halides produce an intense light that penetrates much deeper than the lighting produced by fluorescent tubes. However, metal halides get exceptionally hot, which means a tank with this source of lighting will also require a cooling fan to maintain the correct water temperature. Metal halides are also more expensive than fluorescents to purchase and to operate.

For most fish-only aquariums, six to eight hours of light a day is ample. This amount of lighting will give the fish a predictable night and day cycle and allow them to feed by light. Keeping the amount of hours to a minimum will help to save on your energy costs and keep the algae in the tank at bay.

A mini-reef aquarium should be lit for about 10 to 12 hours every day. This schedule can be tweaked according to the way the organisms in the tank respond. Some may require slightly more or less light.

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