Species guide
Chlorella
Chlorella is arguably the most-cultivated microalga in the world — a genus of small spherical green cells that grow fast, tolerate abuse, and pack serious protein. It is the freshwater counterpart of every marine workhorse in our guides, and the organism that taught most aquaculturists what a healthy green culture looks like.
- What it is
- A genus of small, non-motile, spherical green microalgae — among the most cultivated organisms on Earth.
- Taxonomic group
- Chlorophyta (green algae); Chlorella vulgaris is the classic cultivated species.
- Typical appearance
- Small green spheres, single or in loose clusters; no flagella.
- Typical size
- Cells roughly 2–10 µm across depending on species and strain.
- Culture characteristics
- Fast-growing and tolerant; freshwater species dominate, though some strains tolerate brackish water. Usually grown in closed systems because grazers can clear open cultures.
- Major applications
- Human food and supplements, freshwater live-feed production (rotifers, daphnia), green water for freshwater larviculture, research biomass.
- Typical users
- Supplement producers, freshwater hatcheries and hobbyists, live-feed rooms, cosmetics and biotech research.
Why aquaculture values it
In freshwater aquaculture, Chlorella is what Nannochloropsis is to marine work: the hardy default green-water alga. It feeds rotifers and daphnia directly, greens tanks for freshwater fish larvae, and survives conditions that would end delicate flagellates. The thick cell wall that complicates human digestion is irrelevant to grazers, which crush cells efficiently.
Nutrition and important compounds
Chlorella is protein-dense (commonly half or more of dry weight, strain-dependent) and contains the 'Chlorella growth factor' promoted in supplements, along with chlorophyll and carotenoids. It is not a significant source of the long-chain omega-3 fatty acids (EPA/DHA) marine aquaculture prizes — its lipids are generally shorter-chain.
A note on culture parameters
Growth parameters vary widely between species and strains — Chlorella is a genus of many physiologies. Published numbers for light, temperature and productivity differ by context; start from a strain-specific recommendation and calibrate to your own culture.
Frequently asked questions
Is Chlorella good for marine tanks?
Some brackish-tolerant strains are used, but classic freshwater Chlorella does not thrive at full marine salinity. Marine green water usually uses Nannochloropsis or Tetraselmis instead.
Why is Chlorella grown in closed systems?
Small grazing zooplankton can demolish an open Chlorella culture quickly. Closed or covered culture keeps grazers out.
Chlorella vs Spirulina — which is better?
Different organisms for different purposes. Chlorella is a freshwater spherical green alga; Arthrospira is an alkaline filamentous cyanobacterium. Both are protein-rich foods; neither is universally 'better'.