Light Requirements for Aquarium Plants

Healthy aquarium plants require a regular cycle of daily light and dark in order to maintain lush growth and vibrant color. Using a timer helps assure an adequate duration of light. A minimum of 10 to 12 hours of light of the proper intensity is the most beneficial and allows the process of photosynthesis to occur. Lights left on for too long encourages unsightly algae growth that can be difficult to remove.

  1. High Light Plants

    • Aquarium plants that require high lighting conditions do not fare well in tanks with insufficient light levels. Instead of flourishing, they droop, lose leaves, stop growing or die. Plants that require high or bright light levels include hornwort, giant hygro and banana plant, among others. Provide 2 to 4 watts of light per gallon of water in a tank that is less than 24 inches deep. Fluorescent full-spectrum bulbs offer the most beneficial light and encourage plant growth while enhancing fish color at the same time. If your tank bulb does not provide enough high-intensity light, do not run the lights for a longer period of time, as this will not increase the intensity of the light. Instead, add another bulb to your tank hood. If the hood will only accommodate one bulb, upgrade it to a two-bulb model. Using two bulbs increases the light intensity in the tank without adding hours to the light cycle.

    Medium Light Plants

    • Plants that require medium lighting conditions sometimes thrive even when lighting levels are not consistent and they often respond well to brighter light levels. However, exposure to lower-lighting levels for extended periods of time adversely affects some types of medium-light plants. Medium light plants include water wisteria, anachris and Amazon swords. Broad-spectrum fluorescent bulbs produce adequate levels of light for these plants. Changing out the bulbs every six to 12 months helps maintain a consistent level of light, as the bulbs lose intensity as they age.

    Low Light Plants

    • Failure to receive enough lighting in the proper intensity and duration can harm or even kill many aquarium plants. However, there are plants that thrive in low light levels, and these plants suffer if they are exposed to light levels that are too high. A few low light plants are java moss, giant Salvinia and some types of anubias. While some low light plants will thrive in slightly higher light levels, such as medium-intensity lighting, they prefer lower light intensities. Aquarium hoods that hold only one fluorescent bulb will provide sufficient lighting for low light plants.