Step-by-step: Get Started with Your First Microalgae Culture

Getting Started with Your First Microalgae Culture

Starting a microalgae culture doesn’t require a lab full of expensive equipment. With a few simple tools and good habits, you can grow a healthy suspension culture right at home.

What You’ll Need

• 1 transparent, clear PET plastic bottle (1–7 L)
• Drill or punch to make 6 mm holes
• Silicone tubing and a bubble stone for aeration
• A small aquarium pump (or other gentle air supply)
• Filter wool or cotton for a basic air filter
• Low sodium mineral water (room temperature, 21–28 °C)
• Your starter algae culture (50 mL to begin)

Step-by-Step Setup

1. Prepare the bottle
   • Drill a 6 mm hole in the cap for the air tube. The tubing should reach the bottom of the bottle, with a bubble stone attached.
   • Make another small hole in the cap for pressure release. Cap it loosely with filter wool or cotton to prevent contaminants.
2. Clean thoroughly
   • Rinse the bottle with hot water or a mild bleach solution to kill contaminants.
   • ⚠ Important: Rinse very thoroughly afterwards with non-chlorinated water (boiled and cooled tap water or mineral water) to ensure no chlorine remains, as it can kill your algae.
3. Add water and culture
   • Pour in 50 mL of low sodium mineral water at 21–28 °C.
   • Add 50 mL of your algae starter culture.
4. Provide light
   • Give about 8 hours of natural light daily, or use artificial light in the chlorophyll A + B range.
   • Avoid direct harsh sunlight that can overheat the bottle.
5. Daily care
   • Maintain the light cycle.
   • Gently shake the bottle each day to keep the algae in suspension (before you set up aeration).
6. Dilution for growth
   • After 7 days, dilute the culture with an equal amount of mineral water.
   • If the culture volume is getting large, switch to a bigger container.
7. Repeat & scale
   • Repeat steps 4–6 until you have ~1 L of culture.
8. Aeration for peak growth
   • Once at your desired scale, connect the air pump and bubble stone for continuous gentle aeration. This ensures good CO₂ uptake and constant mixing.
9. Harvesting
   • To harvest, remove a portion of the culture and replace it with fresh mineral water to keep the population stable.

Medium Options

For beginners, low sodium mineral water is a safe, universal choice.

There are a multitude of different purpose culture medias available, for example, on the UTEX website.

Measuring Growth with a Secchi Ruler

The soft plastic Secchi ruler (available here) has its tip bent at 90° and fitted with a mini Secchi disc. You can use it with the 50 mL centrifuge tube (comes with the culture) for consistent, comparable measurements.

How to use:

1. Fill the 50 mL tube with your algae culture.
2. Hold the Secchi disc end in the tube and look from above in the same natural light each time (to avoid brightness differences).
3. Lower the disc until it disappears — read the depth on the ruler.
4. Record this reading in a logbook with the date and any notes about light, temperature, or dilution.

Markers on your ruler:

• Upper red mark: Harvest limit — above this density, growth slows and oxygen exchange suffers.
• Lower red mark: Maximum recommended dilution for Chlorella under normal indoor light — below this, growth can stall.

By staying between these red marks, you can maintain healthy growth without overcrowding or starving the culture.