Different wattages of lighting systems will produce different light intensities. Because of this, a general watts/gallon recommendation is a poor guideline to use for a reef aquarium. For example; a 48", 54W T-5 fluorescent bulb emits light approximately 4 times more intense than light from a 48", 40W T-12 fluorescent bulb with nearly the same wattage. Another example is light intensity emitted from Metal Halide and HQI bulbs. Some organisms that originate in the shallow waters of the reef in nature require light intensity similar to that of the sun. These two bulb types reproduce the very high intensity light that can be neither duplicated by another system nor be financially feasible to be duplicated by another system.

The following recommendations are for aquariums that are 24" deep or less. For taller aquariums, compensate by providing a higher amount of wattage per gallon using the chosen lighting system, or by using a more intense lighting system.

Low:
Species that fall into this category include non-photosynthetic species, species that originate in the deep parts of the reef or from turbid waters or ones that grow underneath overhangs and ledges.

Provide a lighting intensity of 1-2 watts per gallon. For most aquariums, except the very large systems, standard fluorescent lighting is ideal. Provide a 50/50 mixture of daylight and actinic lighting.

Moderate:
Moderate lighting levels duplicate the mid depths of the reef in nature, and represent the lighting requirements of a large number of the corals and invertebrates offered. Species that fall into this category are very flexible in regards to the lighting conditions. For example, they can be placed at the top of an aquarium with low-moderate lighting, or at the middle to bottom of aquariums with high lighting.

Provide a lighting intensity of 2-4 watts per gallon using Compact Fluorescent Lighting, VHO or T-5 Fluorescents. Illuminate the aquarium using a 50/50 mix of daylight and actinic lighting. For larger aquariums, consider using Metal Halides to cut down on bulb replacement costs.

High:
Most of the corals and invertebrates in this category originate from the shallow, pristine waters of the coral reef. They demand intense lighting along with good water flow and low nutrient levels. Because of these requirements, the Care Level for most of these corals will be "Difficult" to maintain. However, given the right conditions, they can be the fastest growing, most colorful corals in the aquarium.

Provide a lighting intensity of 4-8 watts per gallon using a combination of Metal Halides or HQI's, along with Compact Fluorescent Lighting, VHO or T-5 Fluorescents. The spectrum of the Metal Halides will depend greatly on personal preference, but should be between 6,500°K (reddish yellow) and 14,000°K (blue/white). Use actinic bulbs for the supplementary fluorescent light fixture in a ratio of 1/3 to1/2 of the total wattage of the system. These actinic fluorescent bulbs can then be set on a timer to simulate both dusk and dawn on the reef.

Please Note: The lighting systems recommended for light-loving corals and invertebrates that fall under the "High" light category, produce a large amount of heat. Cooling fans and possibly a water chiller is a necessity when using these lighting systems.

These recommendations for lighting systems and intensities are general due to the variances in aquarium set-ups. Situations that will affect the intensity of lighting systems include type of canopy on aquarium, distance of bulbs from the top of aquarium, water clarity and the type/brand of ballasts and bulbs used.

Keep in mind that the selection of species compatible to your aquarium is not always limited by your particular lighting system. For example, if your aquarium system provides high light conditions, a species that requires low lighting can still be incorporated into the aquarium by placing it near the bottom of the aquarium and out of direct light.

Use these guidelines when choosing the species for your aquarium and most importantly monitor the health of the corals and invertebrates. Light intensities change dramatically throughout the same aquarium, so moving the specimens to a different location in the aquarium may become necessary. It is important to allow the organism to adjust to the new location and lighting conditions prior to making judgment on its health.