Metal Halide Aquarium Lighting
Choosing what kind of lighting is appropriate for you aquarium depends on what is required for the plant and animal life you have in your tank. The right light intensity is important for sustaining corals and invertebrates in your aquarium. This is due to their dependence on photosynthesis to generate energy and food. While there are many options for lighting systems for your aquarium, if you have invertebrates such as clams, sea anemones or some types of coral, metal halide aquarium lighting would be your best bet because of the light intensity required for these animal to sustain themselves and thrive.
Why Metal Halide Aquarium Lighting? You are in essence recreating a natural habitat in a small space for the plants and animals you have selected. If you're recreating a reef and have SPS corals, clams, sea anemones and other invertebrates, you need the high intensity of metal halide aquarium lighting. In this family, there are two kinds of bulbs available to purchase. The first is the single ended bulb, usually either referred to as either mogul based or SE bulbs. These bulbs look like normal light bulbs but have a thicker single thread and will fit in a mogul light socket. They are available in 175, 250, 400 watt bulbs but can also be available in 150 watts and 1000 watts as well. An outstanding feature of the mogul bulb is the glass tube around the arc tube (the part of the bulb that lights up) that is in place to protect the bulb from splash and breaking as well as provide UV protection, eliminating the need for an additional glass barrier when placed inside the tank. Mogul bulbs are the most widely available and used metal halide bulbs.
The other type of metal halide aquarium lighting is the double ended or DE bulb. Instead of having a single thread and UV protection, DE bulbs are held in place with two ceramic end caps. These snap onto the bulb itself and are housed inside another enclosure that has UV protective glass. DE bulbs are available in 70, 150, 250, and 400 watts. They are relatively new to the industry but are gaining popularity due to their light levels being higher than those of a mogul bulb of comparable wattage.
What kind of wattage to choose depends on the depth of your tank and what your corals needs are. If you choose to use a mogul or SE bulb and you have a tank that is 18 inches or less, it is recommended you use a 175 watt bulb. For aquariums between 18 to 24 inches deep, use a 250 watt bulb. For tanks 24 inches or deeper, you should use a 400 watt SE bulb. Placement of these bulbs depends on the tank depth as well in relation to the corals you have. Place a 175 watt bulb about 5-10 inches from the coral or 5-15 inches from the coral if you choose a higher wattage. If you decide to use a DE bulb for your lighting, 150 watt bulbs are recommended for tanks up to 22 inches, while tanks 22 inches to 30 inches deep should have a 250 watt bulb. For tanks larger than 30 inches deep, it is recommended you use a 400 watt bulb. Smaller tanks less than 15 inches deep can use a 70 watt DE bulb. Whichever bulb type you decide on, bear in mind water quality and clarity are just as important when choosing a metal halide aquarium lighting system.