Aquarium Lighting for Plants

Live plants can be a great addition to your aquarium. Even beginner-level aquarium hobbyists should have no trouble raising some of the hardier mosses and ferns that are widely (and cheaply) available. But even the easiest-to-grow aquatic plants have some basic needs, one the most obvious being light. A lighting system that promotes the growth of your aquarium plants doesn't have to be intimidating or expensive.

  1. Fluorescent Lighting

    • Many aquarium enthusiasts who grow live plants use standard fluorescent bulbs. They give off more light per watt than incandescent bulbs, don't add uncontrolled heat to the aquarium, and provide the type of light needed for plants to survive. To best approximate sunlight, you can get an aquarium hood with two fixtures and mix two fluorescent tubes with different "color temperatures". For example, one bluish light and one yellowish light. This will cover more of the full light spectrum provided by the sun.

    Grow Lights

    • Grow bulbs are light bulbs that are designed to aid plant growth, and there are some made specifically for use in aquariums. The benefit of using grow bulbs versus normal fluorescent lighting is debatable, but many aquarium and terrarium keepers swear by them. Grow bulbs for aquarium use are available as low-wattage incandescent bulbs, fluorescent tubes, and---more recently---LED matrix designs, which are super-low wattage and provide a distinct and crisp sort of illumination.

    Natural Light (Sunlight)

    • Natural sunlight is obviously going to be the best source of light for any living thing. If you can position your aquarium so that it is well-lit by a window or skylight for at least half of the day, you may not need to bother with plant-friendly aquarium lighting at all. A planted aquarium that receives an adequate amount of sunshine can use regular, inexpensive incandescent bulbs instead of expensive grow bulbs or fluorescent fixtures.

    Amount

    • The question "how much light does my aquarium need?" has two answers: one scientific and one practical. The scientific answer is to provide between a half-watt and 1 watt of light per each liter of water in your aquarium. This is considered ideal for both plants and most fish. The practical answer is to read the lighting instructions that came with your aquarium hood and follow them. Never use a bulb higher than the recommended wattage, as this may cause melting or burning of your aquarium equipment.

    Duration

    • Many novice aquarium owners make the mistake of leaving their lights on 24 hours a day, thinking that this will lead to optimal plant growth. This is not necessarily true. The most beneficial habitat for plants (as well as fish) is one that mimics the natural world as closely as possible. This means leaving the aquarium unlit overnight to simulate nighttime in the wild. Turning off your lights for up to three days at a time can also be an extremely effective way to curb unwanted plant growth---for example, algae outbursts. (Note that turning off the lights for an extended period to battle algae isn't recommended if you have decorative plants in early growth stages.)

    Species-Specific Concerns

    • Every plant has slightly different lighting needs. If you're planting anything exotic or unusual in your aquarium, do some research beforehand to make sure the plant will be tolerant of your lighting setup. Beginners should stick to hardy, tolerant mosses and ferns which can be replaced inexpensively.