Algae are a single-celled, aquatic life form that photosynthesize, with many of the same nutrient and oxygen requirements as plants grown intentionally in CEA/MEA. Algae are difficult to exclude in hydroponic plant production. They are also common in pot culture, although not as visually obvious.
In hydroponic systems:
Most growers accept algae as an eyesore but not a problem as long as it is kept to a minimum. Algaecides (or algicides) exist, but can damage certain plants either by directly damaging roots, or by causing phytotoxicity, or by both. Containers that hold nutrient solution should be opaque so light cannot reach the nutrient reservoir and permit algae growth. If algae are allowed to become established in a nutrient reservoir, it will use both nutrients and oxygen, limiting what is left for crop use. Vessels that contain plant roots should also be opaque to prevent algae from growing on plant roots and damaging them. Hydroponic system components such as troughs in NFT and floats in deep trough systems are often washed with a sodium hypochlorite (e.g., Chlorox®) solution between crops to suppress algae growth.
In pot culture:
Algae growth should be limited by careful control of soil moisture content. Root medium that stays very moist at the surface promotes algae growth on the top of the medium, which can attract problematic pests such as fungus gnats and shore flies.
'Control of Algae in Hydroponic Systems' By J Coosemans, Laboratory of Phytopathology and Plant Protection - Belgium, 1995. In Acta Horticulturae, volume 382, page 263.
**Acta Horticulturae is accessible at http://www.actahort.org/ but there is a charge for articles.**
