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There used to be a very simple rule to follow concerning freshwater aquarium lighting requirements. It was “Use 3 to 4 watts per gallon”. However this only relates to incandescent bulbs and as we all know things have moved on in the freshwater aquarium lighting department!

In order to achieve precise control of freshwater aquarium lighting, light sources are contained in a lighting canopy that sits over the aquarium. It is best to control the freshwater aquarium lighting with a timer for more reliable on/off periods and generally speaking around 12 hours per day of lights on is best. For larger aquariums (more than 3 feet long) where several bulbs or tubes are in use on/off times can be staggered to simulate dawn and twilight.

Sorry, it gets a bit technical here! The amount of illumination that a light source produces is measured in Lux. one Lux is one lumen per square metre. A watt is a measure of how much energy is being consumed every second by the light source and has nothing to do with the amount of the illumination produced. The efficiency of a light source is measured in lumens per watt. So it is nonsense to specify numbers of watts to obtain a certain illumination when we may be comparing incandescent bulbs which are grossly inefficient with fluorescent tubes and even LEDs (Light Emitting Diodes) that are super efficient. This is clearly illustrated if you compare the heat produced by an incandescent bulb and that produced by an equivalent fluorescent tube. The heat represents wasted energy and it is obviously far greater in the bulb than the more efficient fluorescent tube.

The quality of freshwater aquarium lighting is also very important. A full spectrum light source is extremely beneficial to the health of both fish and plants.

A large number of possibilities now exist for freshwater aquarium lighting sources. It is rare to find incandescent bulb lighting for an aquarium now and no one would even consider it for a new installation. A few of the options are listed below.

T-12. This is a the standard pin, one and a half inch wide tube. It typically produces 40 lumens per watt. They are the least expensive option.

T-8. This is a standard pin one inch diameter tube and is the size most often come across in aquarium lighting.

T-5. Generally around 13 mm in diameter, this is a mini pin bulb which generally uses even less watts per lumen than many T-8 bulbs. A common lumens per watt output for T-5 lamps is around 65. The T5 has become very popular among plant keeping freshwater aquarists. They are compact, come in many varieties and high lumen per watt outputs.

T-2. These bulbs are the latest fluorescent technology yet (LED are advancing even more). They measure only 7 mm and allow for several bulbs in a small space. A 13 watt 20 inch T-2 Bulb produces 73 lumens per watt in a very small space with high quality illumination.

VHO Power Compact. This stands for “Very High Output”. They come in T-5 through T-12 standard fluorescent tubes and in the newer power compact.

PC (or CFL). This stands for “Power Compact” or “Compact Fluorescent Lamp (light)”. These bulbs come in straight pin arrangements, square pin arrangements, and the self ballasted standard incandescent fixture “screw in” type. These bulbs are similar to T-5s and have about the same lumen per watt output (generally around 60 lumens per watt).

SHO Power Compact Lights. This newer ‘Power Compact’ is perfect for planted aquariums. In fact probably the best apart from some LEDs. The SHO Light is presently sold in a self ballasted PC bulbs/light. The 105 Watt SHO Daylight bulb puts out 6300 lumens and is comparable to a 525 watt Standard bulb. This comes to 60 lumens per watt. However this is a deceptive guide, because you can fit many more of these bulbs in a given space and also use better reflectors.

LED (light-emitting diode). This aquarium light type uses semiconductor technology as its light source. These lights do not have heat problems, often last 50,000 hours, produce little useless yellow/green spectrum light (in aquarium adjusted configurations), and are very compact.

So there you have it. I have presented the pros and cons of freshwater aquarium lighting sources. The choice is yours but you can now make an informed choice.