HerbLensGo Plus
← Plant library
Plant photo

Photo: Frank Fox, CC BY-SA 3.0 de (via Wikimedia Commons)

Rain Pool Algae

Haematococcus pluvialis

Also known as Blood Rain Algae, Astaxanthin Algae, Hematococcus

At a glance
Family
Haematococcaceae (order Volvocales, division Chlorophyta, the green algae)
Type
single-celled freshwater green microalga
Parts used
whole cells, particularly the red encysted stage rich in astaxanthin
Size
microscopic, individual cells run 10 to 50 micrometers, but a bloom can tint an entire puddle rust red
Bloom
does not flower, it reproduces by cell division and forms thick-walled red resting cysts when stressed
Habitat
temporary freshwater pools, rock hollows, birdbaths, and cattle troughs that fill with rain and later dry out, found in temperate regions worldwide
Acquisition
Buy
This plant in HerbSense

Key benefits

Rich antioxidant pigment source
Traditionally used for skin
Supports eye comfort
Prized for joint ease

Traditional uses

Haematococcus pluvialis is not an old herbal remedy in the way echinacea or chamomile are. It is a tiny green algae that naturalists noticed for centuries turning rain puddles and stone hollows a startling blood red, a phenomenon that gave rise to old folk tales of blood rain long before anyone understood the cause. Only in the twentieth century did scientists identify that red color as astaxanthin, one of the most concentrated natural antioxidant pigments known, and the algae has since become a cornerstone of modern nutraceutical and skincare practice rather than a plant of ancient apothecary tradition. Today it is cultivated deliberately, stressed under bright light and scarce nutrients until it turns that same deep red, then harvested for its pigment.

How to grow & use it

🔒

The full apothecary for Rain Pool Algae

Traditional remedies and step-by-step preparations, a complete growing guide, and how to harvest, dry, and store it, all unlocked with HerbLens Unlimited.

  • Remedies & preparations
  • Growing guide
  • Harvest & storage
Unlock every plant

From under $6 a month. Free plant identifications always included.

Pairs well with
  • Omega-3 fish oil
  • Turmeric
  • Rose hips
Substitutes
  • Spirulina
  • Goji berry
Choose it when

For the deepest red an antioxidant can turn, born from a puddle that dries under the sun and refuses to fade quietly.

Did you know?

The pink of a flamingo's feathers and the rosy flesh of wild salmon both trace back to carotenoid pigments like the astaxanthin this little algae produces, absorbed up through the food chain from the tiny creatures that graze on it.

Safety

Astaxanthin supplements from this algae are generally well tolerated, though they may modestly lower blood pressure, so use caution with blood pressure medication. Never gather red algae from wild ponds or puddles yourself, since it's genuinely hard to tell apart from toxic cyanobacteria blooms; buy from a reputable supplement source instead.