Spirulina Density Chart
Lower a Secchi Stick into your culture until the black and white pattern just disappears. Read the depth. Then use this chart to turn that reading into a dry weight in grams per litre.
Harvest window: a spirulina culture is ready to harvest somewhere around 10 to 15 g/L. Use this chart to tell when you are there without drying anything down.
How to read it
- Find your Secchi reading in millimetres along the axis.
- Read across for dry weight in grams per litre.
- Shallower reading means denser culture. As it thickens, the stick disappears sooner.
- Take the reading at the same time each day and write it down. A single number tells you nothing. A column of them tells you everything.
What dry weight means
Spirulina is a microalga. Separated from the water and dried, it has a mass we call the dry weight, expressed against the volume of water it was growing in, so grams per litre.
How to farm spirulina