Once upon a time, a simple fluorescent bulb was the standard for aquarium lighting. Now, things are quite different. Just looking through a catalog, you may see 5 or more different types of bulbs. Then there are different types of fixtures, some of which even utilize hybrid combinations of bulb types. With all of these options available, how do you know what type to choose? This article will hopefully help you make an informed decision based on what you really need.
The simplest option for your aquarium is no lights. You don't really need lighting if the aquarium is in a bright room or next to a window and you don't have anything in the aquarium that requires photosynthesis. For most people, however, this is not a viable solution.
Once you have made the decision that you need lights, the next step is to determine how much. If you only plan to have fish in the aquarium, you will only require minimal lighting. If you plan to have plants, coral, anemones, or clams, you will need more substantial lighting.
Traditional fluorescent lighting is efficient, but relatively bulky compared to other types of lighting. The T12 bulbs are one and a half inches in diameter, requiring a large light canopy, but they also run cool and won't need active cooling. The drawback is that these types of bulbs have a low light output and won't be the brightest.
Next up, there is High Output (HO) fluorescent lighting. This refers to T5 bulbs, which are able to output much more light than traditional T12 bulbs, yet only require a 5/8 inch diameter. This means you can get more lighting from a smaller area, but you will also have to deal with the increased heat output from these bulbs. Most T-5 lighting systems use built-in fans to remove the heat, so it isn't a big deal. Another benefit with this type of lighting is the multitude of bulbs available with different wavelengths. Everything from actinic to pure white is available, allowing you to mix and match to achieve the perfect color.
The next step in lighting power is Very High Output (VHO) fluorescent lighting. These bulbs are typically sold in T12 format and have an intense light output. Like standard fluorescent bulbs, these are bulky and require a bigger hood or canopy, but will typically not produce as much heat as T5 bulbs.
Right above VHO lamps are Power Compact (PC) bulbs, which typically use the T8 form factor. These bulbs are one inch in diameter, making them smaller than VHO and standard output fluorescent bulbs, but slightly bigger than HO bulbs. These bulbs provide the maximum light output available in fluorescent lighting.
The top of the line is metal halide lighting, which uses bulbs similar to incandescent bulbs, only much much brighter. These bulbs operate with a high pressure gas inside and produce light by arcing electricity. Most bulbs require between 100 and 500 Watts of electricity, making them costly in terms of power usage. These bulbs are also very inefficient compared to fluorescent bulbs and produce massive amounts of heat. However, some aquarists use these bulbs due to their tremendous light output.
One increasingly popular solution is Light Emitting Diode (LED) lighting. These bulbs are actual made using solid state semiconductor electronics and have a very high efficiency. Unfortunately, they are also costly and rigging up a system that is bright enough for your aquarium can cost thousands of dollars. They are still popular for accent lighting, typically for nighttime (moon light) applications.
Now that we have gone over the options available, the question is what do you really need? For fish only applications, you only need standard fluorescent lighting or possibly HO lighting. When soft or LPS corals come into play, you will need at least HO lighting. For SPS corals, anemones, or clams, you might be able to get by with HO lighting, but VHO, PC, or metal halide lighting is much more ideal.
Hopefully this article has been helpful in increasing your knowledge of lighting options for aquariums!