When it comes to hydroponic indoor gardening, there are 5 primary light types on the market: metal halide, high pressure sodium, LED, compact fluorescent, and fluorescent tubes. Most grow rooms use a combination of these to achieve maximum growth.

Metal halide grow light

Metal halide grow light

Metal Halide

Metal halide lights are the most popular light used with indoor hydroponics. They produce heavy in the blue spectrum, which the plant uses to produce foliage. Most growers will use a metal halide during the plant’s primary growth period, then switch to a high pressure sodium bulb when the plant is ready to begin fruiting. Metal Halides should not be used on plants that produce foliage rapidly, such as trellising tomatoes. Metal halide lamps produce a lot of heat, so they should always have proper cooling and ventilation.

High Pressure Sodium

High pressure sodium lights produce light primarily in the red spectrum. High pressure sodium lights are the only grow lights that cost effectively produce high amounts of red spectrum light. It is very common for growers to use a digital ballast, which enables them to switch between metal halide and high pressure sodium on the same reflector. High pressure sodiums produce a high amount of heat, so a proper ventilation and cooling system must be present with any HPS bulb over 400 watts.

LED Grow Light

LED Grow Light

LED Grow Light

LED is a relatively new technology to the indoor gardening world, its primary advantages are very low heat, low energy consumption, and full spectrum lighting. LED lights have gotten very mixed reviews since their debut, some swear by them and some claim the growth rates are reduced by as much as 80% compared to traditional metal halide setups. LED grow lights are very expensive up front, but have a lifetime of as much as 100,000 active hours.

Compact Fluorescent

Compact fluorescents are popular for hydroponic grows due to their cost, availability, and efficiency. High output, full spectrum compact fluorescents can be found at nearly every major hardware store, and cost well under 50 dollars. Due to the relatively low lumen output of compact fluorescents, they are usually only used in very small grows, a single metal halide light could produce the same amount of light as 10 compact fluorescents.

Fluorescent Tube

Fluorescent tubes are the traditional tubes used to light most office buildings, they can be found in full spectrum varieties. Fluorescent tubes are primarily used for lighting clones and very small plants, due to their very low lumen output. To receive enough light from a fluorescent tube, every part of the plant’s foliage much be within 12 inches of the tube. Fluorescent tubes produce low heat and can cover a large surface are of small plants, so they are commonly used for lettuce and other leafy veggies grown hydroponicly.