How to Culture Phytoplankton

Phytoplankton is the foundation of every live food chain in reef tanks. It feeds copepods, rotifers, clams, corals, and filter feeders — and culturing your own is cheap, simple, and sustainable.

What You’ll Need

1. Clean culture container (5–20L is common)

2. RODI saltwater (1.018–1.023 salinity)

3. Starter culture (e.g. Nannochloropsis, Isochrysis)

4. culture medium/fertiliser (like Guillard’s F/2 or walnes)

5. Light source (6500K or grow light)

6. Gentle aeration (rigid tube or airline tubing)

7. Optional: Timer, thermometer, lid

Steps

1. Fill your container
Use clean saltwater. Add your fertilizer as directed.

2. Add phytoplankton
Pour in your starter culture. Shake it well beforehand to ensure even cell distribution.

3. Aerate & light it up
Use continuous aeration to keep cells suspended. Light it 16–24 hours/day. A cheap LED or sunlight works fine.

4. Wait & watch
Over 5–7 days, the water will darken. That’s your phytoplankton multiplying. Avoid overgrowth as this can cvauses cell shading, nutrient depletion and cell lysis(death).

5. Harvest & feed
Once it reaches a rich green/gold/brown, pour off what you need through a sieve if feeding pods. Replace with new saltwater and dose more fertilizer.

6. Maintain or split
Split cultures weekly to avoid crashes.

Tips

1. Keep the culture moving — stagnant phyto dies

2. Use different strains for broader nutrition

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