T5 Aquarium Lighting Vs. Metal Halide

With the recent introduction of new t5 lamps, which are capable of replicating the spectrum of light corals need to grow, there has been much debate over whether t5 is better than metal halide.
    • Replicating the sun's intensity with home lights

    History

    • Traditionally, if you wanted to house coral in your home aquarium, you had to have metal halide. They were hot, used anywhere from 250 to 400 watts per bulb, and you still needed florescent atinics (bulbs with a blue color) to get the full spectrum of light corals needed.

    Coral

    • Coral needs high amounts of light to survive because of the algae living in the coral's skin. The algae is known as zooxanthellae. The algae is microscopic and needs light to photosynthesize just like plants in a garden. According to the NOAA, the corals and algae have a mutualistic relationship. The coral gives the algae a protected place to grow and things the algae needs for photosynthesis, while the algae gives the coral oxygen, helps the coral remove waste and gives the coral food.

    Light

    • There are many ways to measure light. According to Sun Master, Photosynthetically Active Radiation is the spectrum between 400 and 700 nanometers. To the algae living within the coral, that is the only light that matters. PAR can be expressed in watts, which is how comparisons are done.

    Metal Halide

    • On the downside, metal halide bulbs are hot, have to be replaced every eight to 10 months and suck up power. One metal halide bulb might use 400 W. You will have to run your air conditioner more often and be wary of splashed water, as the the bulb could shatter. The PAR rating for a 400 W bulb, according to sun master, is 140 W or 35 percent efficiency. On the upside, metal halide bulbs penetrate the water further than t5, making them a necessity for deep aquariums. They also create a "shimmering" effect, like that of the sun on a shallow water reef dive.

    T5

    • T5 run cooler and are more energy efficient than metal halide. You can put them closer to the water because of the cooler temperature, and not have to worry about buying a chiller for your aquarium. The average par rating of a 54 W t5 lamp is 33 W or 61 percent efficiency. T5 lamps have to be replaced around once every 24 months.

    Conclusion

    • If you have an extremely deep reef tank, a chiller, don't mind a jump in the electric bill and are growing Small Polyp Stony Corals, which need extreme amounts of light, metal halide is required for the time being. If your tank is no higher than 24 inches or SPS coral is only kept near the top of the tank, T5 could be the lamps for you.