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T8 and T12 Aquarium Lighting - What is it, Pictures & Forum

Brief Description

Fluorescent aquarium lighting comes in all different colors and sizes. When choosing the right lighting system for your aquarium you should fully understand all of the options before making a decision. One of the most common lighting size options is the T12 light fixture. This fixture is being replaced more and more by a smaller more efficient version called T8 fluorescent lights. This article will explain the differences in cost and efficiency between the T12 and T8 light fixtures.


T12 fluorescent light bulbs are 1.5” in diameter. These light bulbs are run on magnetic ballasts that are there to limit the amount of electrical current running through the bulb. The magnetic ballasts are not as quiet or as efficient as electrical ballasts. T8 light bulbs are 1” in diameter and run on electrical ballasts. When compared to the T12 bulbs, T8 fluorescent bulbs have an illumination output that is more efficient. The T8’s slimmer design allows the illuminating gasses to run more efficiently while using less wattage.

Both T12 and T8 lighting options are available in a variety of different lengths to meet your aquatic needs. From as short as two feet in length to as long as six feet, there are many choices to customize your own aquarium lighting.


Since the T12s were the standard sized bulb used for a long while, the lighting fixtures, bulbs and ballasts are slightly more available than all the equipment needed for the T8 lighting system. There is a conversion option for T12 if you want to change over to T8 bulbs. The initial cost of conversion might not be an attractive option but it pays off in the long run when you save on the amount of electricity used to power the T12s. Since the T12 light bulbs run on magnetic ballasts, they consume more wattage making them less energy efficient than the T8s. When starting from scratch the T8 lighting option can be a little more expensive to purchase outright than the T12 lighting option. Once again, the money saved on electrical cost should more than make up for it over time.

Advantages and Disadvantages

T8 fluorescent light bulbs have a smaller diameter than the T12 lighting system. Despite the sizing difference of the two bulbs they still put out roughly the same amount of lumens. Because of the smaller diameter of the T8 bulbs, more of them can be packed into the same canopy than the T12 bulbs. This is a preferable solution for larger, deeper aquariums because it results in an overall brighter illumination making it perfect for plant life, corals and invertebrates.

T12 light fixtures run with magnetic ballasts which is less energy efficient than the T8 option that runs with electrical ballasts. The magnetic ballasts cost more to operate than electrical ballasts and can be quite a bit noisier while running. The T8 light bulbs run cooler and provide superior light and color quality. This allows for a more natural lighting in the aquarium than can be provided by the T12 light bulbs.

The only negative feature about the T8 lighting option is that the replacement bulbs are not as readily available in aquatic retail stores. There may be less available color, size and lumen options in the store so shopping for them online could be your only option. The good news is lighting manufacturers are gradually moving away from the old technology and replacing it with the newer more efficient lighting options. In time the T8 replacement bulbs should be more readily available through local aquatic retailers.


When deciding to convert your T12 lighting fixture into a T8 lighting fixture you might be a little hesitant when you hear how much it will cost. The silver lining is T8 will pay for itself in approximately three years because of how efficiently this lighting option runs. You will end up saving more money on replacement bulbs and electricity when you switch from T12 to T8.

To convert from T12 to T8 lighting fixtures you will need to replace the magnetic ballasts with electrical ballasts. The end caps will also need to be switched out so that slimmer T8 bulbs can be used in place of the thicker T12 bulbs. You will need to be sure not to exceed the maximum wattage allowed by the fixture or it could present a fire hazard.


Aquarium lighting spectrum picture 1 Aquarium lighting spectrum picture 2 T8 aquarium lighting, picture 1 T8 aquarium lighting, picture 2 T8 aquarium light cover, picture 1 T8 aquarium light cover, picture 2 T8 aquarium light with box picture

Recommended reading about Aquarium Lighting

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