Fluorescent Lighting
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Introduction
Fluorescent tubes (or lamps) are by far the most common and cheapest lamps used in both freshwater and marine aquariums, often being included as standard fittings in "all-in-one" style aquariums.
Fluorescent lighting works by exciting a gas inside the tube by passing electricity through it. The atoms in the gas then release electrons, which strike inside of the tube, which is lined with a powder which emits light (fluoresces) when struck by the electrons. It is this light which is the output of a flurescent tube.
Fluorescent tubes come in a variety of colour temperatures, as well as Actinic. The standard fluorescent tubes you would buy in a hardware store or general lighting store will likely have a colour temperature of 6500K or lower - colour temperatures of 10000K and 20000K are more commonly used in marine aquariums. Actinic tubes are a blue/purple lamp which have a high ultra violet component. The overall effect is similar to a black light, and will highlight the fluorescent pigments on the aquariums inhabitants.
Most fluorescent tubes require external ballasts to run - T8 and T12 tubes also, if using magnetic ballasts rather than electronic, require starters as well, in order to generate the high voltages required to start them.
Types
The main types of fluorescent tubes are T5s, T8s, T12s and Power Compact. Each type of tube has its own particular characteristics.
T5
T5 fluorescent tubes are so named because they are five eighths of an inch thick. T5 tubes are a different length to the "standard" T8 and T12 tubes, use a different mounting system - the pins on the end of each tube are much closer together than on T8 and T12 tubes, and also require electronic ballasts. These differences mean that T5s are not a simple drop-in replacement for T8 and T12 tubes.
T5 tubes are currently available in three output ratings - HE (High Efficiency), NO (Normal Output) and HO (High Output). It is the HO style of T5 tubes which are most commonly used in marine aquariums, as for a given length, they have a higher light output than T8 or T12 tubes. The wattage of T5 HO tubes for the "equivelent" length of T8/12 tubes is show below:
- 2' = 24W
- 3' = 39W
- 4' = 54W
- 5' = 80W
In order to get the best light output from T5 tubes, special parabolic reflectors are often used - when used with such reflectors, similar light levels can be achieved for a given input wattage as when using metal halide lighting, although there are differences in the overall lighting characteristics - mainly in distribution (evenly spread out for T5s verses a "point" light source with metal halides).
Gallery
 From left to right: |
T8
T8 fluorescent tubes are so named because they are one inch (or eight eigths of an inch) thick. These are the most common style of fluorescent lamps, are sold by length rather than wattage (coming in standard sizes of 1, 2, 3, 4 5 and 6 foot, the longer the tube the higher the wattage).
T8 fluorescent tubes are used in NO (Normal Output), HO (High Output) and VHO (Very High Output) modes, with standard lamps overdriven in the HO and VHO modes, often by electronic ballasts (such as the IceCap 660 ballast).
T12
T12 fluorescent lamps are so named because they are 1.5" (or twelve eigths of an inch) thick. They are the same length as T8 lamps, and use the same mounting system, being swappable in cases where waterproof endcaps (which are tightly fitted to the tube thickiness) are not used.
Power Compact
Abbreviated as PC. Power Compact tubes are basically "folded" or "doubled over" flourescent tubes, fitting the length of a tube into a shorter (but wider) package. Power Compacts are sometimes available in a "twin" colour package, with each side of the folded tube lighting up a to a different colour temperature. In this way, a single CF tube can have for instance both 10000K and Actinic lighting properties.
Gallery
Resources
- Actinic Lighting - Reefs.org
- Flourescent Ballast / Endcap Wiring Diagrams - Reefs.org
- IceCap VHO and MH Ballast/Bulb Wiring Diagrams - Reefs.org
