The amount of light required depends on what type of livestock you want to keep. A very colorful selection of corals can be grown under two VHO fluorescents, or four RO (regular output) fluorescents covering the length of your aquarium. Examples of corals that will do well under this scenario are mushroom anemones, bubble tip anemones, bubble coral, zooanthids, star polyps and other polyp colonies. If you would like a greater variety of species, and possibly a more natural looking aquarium, metal halide or a metal halide/fluorescent combination would be more desirable. Metal halides will give the water column the same glitter effect as the sun, and also enable your system to support higher light loving corals (e.g. most Acropora sp.). As a rough guideline, a low to medium light system uses 2-5 watts of light per gallon, and a medium to high light system uses 5-10 watts per gallon. Corals requiring low light can be kept in high light systems, but may have to be positioned accordingly.

How many metal halides do I need for my sized tank?

The quantity of metal halide bulbs is first determined by applying the "watts per gallon" guideline (see question/answer above), and then by the length of your tank. For evenness of light color across the length of the aqarium, approximately one metal halide per two feet of tank length is suggested. For example, a 55-gallon regular (48" long) could easily accommodate two metal halides, but a 55-gallon hexagon (24" long) would only accommodate one metal halide. If evenness of light is not necessarily required or desired, a 6-foot tank may be maintained with only two metal halides, resulting in "shadier" zones toward the ends.

What is color temperature?

Color temperature, or degrees Kelvin (°K), is a number assigned to a bulb to describe the color of light it emits. The lower the number the warmer or more to the orange/yellow side of the light spectrum is its appearance. The higher the number the cooler or more to the blue side of the light spectrum.

Here are some °K examples and their corresponding color descriptions:

When is supplemental fluorescent lighting desired or needed with metal halides?

Some metal halides produce the proper spectrum of light to stand alone. However, to achieve full enjoyment out of viewing your fish and corals in the colors as they would appear in the ocean at depths of about twenty feet or less, you should use the following guidelines:

Is heat from lighting detrimental to my aquarium?

Heat is not a problem when using RO fluorescents. When using VHO or MH lighting, however, fans should be installed in your canopy. Chillers are not necessary in most areas, although they are recommended for any system where the air temperature in the room housing your aquarium consistently rises above 90º Fahrenheit.  Heater settings may need to be adjusted up when adding a metal halide lighting system in order to narrow the daily temperature fluctuation.  Temperatures between 79-84º are OK.

How long should my lights be on?

How long will my bulbs last?

Fluorescent bulbs should be changed every six months, and metal halide bulbs every six to twelve months depending on the bulb type and coral requirements.

The industry standard for a "six-foot" fluorescent tube is actually 69.75" from end to end; with end caps the overall length is 70.5".

If my canopy interior isn't long enough to accommodate standard VHO or RO fluorescent bulbs to cover the length of my tank, what can I do?

Our lighting systems can be made in shorter lengths to accommodate these situations. We offer SpaceSaver VHO bulbs available to fit interior canopy lengths of 22", 34", 46", 58".

There are several reasons why we recommend VHO fluorescent tube lighting over compact fluorescent bulbs.  First, compact fluorescent bulb lengths aren't as well suited for most stock aquarium lengths.  Secondly, contrary to some posted info, we have found electronically ballasted VHO bulbs last longer than compacts, and can also be dimmed with an added dimmer.  Also, VHO bulbs are less expensive, and the very small output increase that the compact fluorescent bulbs have over VHOs is not significant enough to give up the benefits of VHO lighting.  For a comparison in light output, see our Technical Data page.

How do I know what a specific bulb or combination of bulbs will look on my tank?

For a visual demonstration of various bulbs in a variety of combinations, including metal halide alone, and metal halide/VHO combinations, please see our Bulb Color Comparison page, as well as our Featured Reef photo gallery.

How long does it take to get my order?

Light bulbs and accessories are usually shipped the next business day following date of order, with your choice of FedEx ground or FedEx express service.  Lighting systems are built to order, and are shipped within 10 days of order placement.

This is a difficult question to answer, because different bulbs are most appropriate for different situations.  Things to consider would be tank dimensions, depth you are trying to simulate, and whether or not supplemental bulbs, multi-staging and/or dimming will be used.  Given an aquarium of 100 gallons or less, with a height of 24" or less (simulating shallower water), and the ability to house a full variety of corals, I would recommend the 6500K 150W Iwasaki bulbs, along with 2xVHO actinic fluorescents.  If you are not interested in multi-stage lighting, but prefer metal halide only, there is a new 50000K 150W Aqua made by Iwasaki that I am currently testing.  This bulb has a pleasing look all by itself, and according to initial data, looks very promising.  See a side by side comparison of these bulbs on our Technical Data page.

What type or style of lighting system is best for me?

Personal preference, long and short term goals for your aquarium, and budget all play a factor in determining what is best for your lighting system needs. When you are ready to make those decisions, we hope you’ll give us the opportunity to offer our solutions to your lighting needs. 

Copyright © 2000-2007 Coral Reef Eco-Systems
Last modified  Saturday, 26 January 2008