Aquarium Light Metal

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October 19th, 2008 admin Leave a comment Go to comments

Aquarium Light Metal
WHAT IS THE DIFF. BETWEEN T5 AND METAL HALIDE LIGHTS? WHAT WOULD BE BETTER FOR A REEF AQUARIUM?

T5 = Fluorescent lighting with bulbs that are 5/8" diameter. These bulbs are smaller than standard T8 and T12 fluorescent bulbs. Therefore more bulbs can be fit into the same space as the larger diameter bulbs.

The efficiency of T5 bulbs is largely dependent upon the quality of the reflectors used. The cheaper, less expensive T5 fixtures use a single flat piece of aluminum above the bulbs to reflect the light downward. The better reflectors are up to 300% more effective. They are single reflectors above each individual bulb. The shape of these better reflectors are parabolic in shape and highly polished. The parabolic shape takes the light that shines out of the top of the T5 bulb and 'bends' it around the bulb and down into the tank. The cheaper flat piece of aluminum just takes the light emitted from the top of the T5 bulb and reflects it straight down, basically back into the bulb itself, rendering that light useless, for the most part.

T5 lighting is also a linear source of light. Therefore the light is emitted from the length of the fluorescent tube and more evenly distributed within the aquarium.

The heat generated by T5 lighting is much less than the heat generated by MH lighting. It is still important to keep the T5 bulbs cool by running a fan across the bulbs. Keeping the bulbs cool will help to extend the life of the bulbs and lengthen the replacement period.

T5 lighting is adequate for any of the marine animals we keep in our tanks. The downside to T5's is the intensity of the light at depths greater than approx. 22"-24". For taller tanks it is either recommended to use MH lighting or strategic placement of your corals. Arranging higher light demanding corals in the upper 1/2 of the tank and the lower light demanding corals on the lower 1/2 would permit you to use T5 lights on tanks taller than 24". Just be realistic with your expectations and use the above strategy to compensate for the T5's shortcomings.

MH = Metal Halide lighting. This is a very intense, point source of light. Comparing it to a T5 bulb trying to create an apples to apples type of comparison, you'd either have to stretch out the MH light to emulate a T5 bulb, or shorten the T5 bulb so that all the light would come from a single point. The MH lighting being point source, decreases in intensity as you move from left or right from the center point directly below the bulb.

MH bulbs typically lose their efficiency in 7-9 months depending upon how many hours a day you run the bulb. Heat output from a MH bulb can easily burn a person, badly. Therefore it can also burn or 'bleach' a coral if you are changing from a less intense source of light to MH without acclimating the new MH lights. In other words, if you want to change from power compacts, T5's, dare I say incandescent, etc., it is important to either raise the height of the MH Fixture/pendant and/or shorten the photoperiod the MH light is on. Strategically increasing the photoperiod over the course of a couple of weeks and/or lowering the height of the fixture should acclimate your corals and inverts to the new, more intense light.

MH bulbs are designed with varying wattages to allow for different tank designs. They primarily come in wattages for aquariums in 70w, 150w, 175w, 250w, 400w and 1000w. Bulb type also varies between SE (Single Ended) and DE (Double Ended) mounting styles. The last varying factor in MH bulbs is the kelvin rating they emit. The lower the kelvin rating 5000K, 6500K are more in the yellow/red spectrum, and bring out those colors in the animals in our tanks. The middle range of the spectrum is in the 10000K, 12000K, and 14000K range. These bulbs are more of the crisp white spectrum. Then we've got the 15000K, 20000K and even some 22000K bulbs on the market. These are the bulbs that bring out the blues in our corals.

Many people like to use a mixture of MH bulbs in the 10K-14K (same as the above kelvin ratings eliminating the three zeroes) to bring out the crisp white, or daylight spectrum as if the sun were high in the sky, with T5 bulbs in the 20K range. Using a combination of bulbs like this makes it very easy to simulate an effective sunrise/daylight/sunset lighting period.

MH bulbs produce a Lot of heat and can easily cause aquarium temperatures to rise to unhealthy levels. Therefore it is important to take into consideration the ambient room temperature where the tank is located. If you run A/C in that room during the warm/hot months and the room temperature remains in the 70-75 degree range, you might be ok. If you don't run a room/house A/C while you're not home, and the room your tank is in can rise to the 80-85 degree range, you may need to get yourself an aquarium chiller. This can also be true for T5's, but more likely to happen with MH bulbs.

Great source for reef lighting is Saltwater Critters. See the links below.