T5 High Output (HO) lighting system designed to be mounted into a canopy.
High output T5 (skinny straight bulb) fluorescent lights are much brighter than standard fluorescent lights. They have become a very popular lighting choice for aquariums 36 inches (90 cm) or longer. T5 light fixtures come in many different sizes, but the most common are 24 inch/24 watt, 36 inch/39 watt, 48 inch/54 watt, and 59 inch/80 watt. T5s are capable of keeping nitrate levels near 0 ppm in planted aquariums. It is recommended that you have two bulbs running parallel to each other per 6 inches (15 cm) in aquarium width. In other words, if your aquarium is 12 inches (30 cm) wide, you should have four rows of bulbs. T5s are good lights to use on aquariums up to 24 inches (60 cm) in depth. The 54 inch/80 watt bulb is an excellent choice for 60 inch (150cm) long aquariums, like standard 100 gallon aquariums. T5 lights do generate heat, and may need the addition of a fan to keep heat transfer to the aquarium minimized.
Catalina Aquarium's 15 inch LED light system.
LED lighting systems are the newest lighting solution for aquariums. They do produce a shimmering effect much like metal halide lighting. They produce very little heat under the light, but the electronics that power them can get very hot. If a LED retrofit lighting system is mounted in canopy, fans may be required to help vacate heat. Reviews on this type of lighting system have been mixed. How many LED lights you need for a given space is very subjective since all the manufacturers use different configurations. Individual LED lights cannot be replaced when they burn out as they are part of an array on a board. How well they work in controlling nitrate accumulation in comparison to other high output lighting systems is still unknown.