Absorption Spectrum of selected primary and secondary pigments. Pigments are proteins available to capture specific photon energy vital for photosynthesis.
Light - photon energy - is the single most important factor to consider for growing algae. Photosynthesis is the primary mechanism driving algae growth and its importance to commercially growing algae is dominant. Algae require specific wavelengths of photon energy ranging from 400 nm to 700 nm.
This Photosynthetic Active Radiation (PAR) light refers to the broad spectrum of wavelengths to which pigments respond. All oxygenic photosynthesis on Earth happens, and is driven by wavelengths between 400 nm and 700 nm - not even one "octave" of light frequencies - a very narrow band given the wide electromagnetic spectrum.