DIY Culture

🌱 How to Culture Phytoplankton – Step-by-Step Guide

Phytoplankton is essential for feeding filter feeders, copepods, corals, and more. Culturing it at home is cost-effective, sustainable, and surprisingly easy with the right setup. Here's how:

🧪 What You’ll Need

Equipment:

  • 1-gallon to 5-gallon container (clear plastic jug or bucket)

  • Air pump with airline tubing

  • Light source (LED grow light or fluorescent bulb)

  • Timer (for consistent light cycles)

  • Graduated cylinder or measuring cups

  • Thermometer (optional but helpful)

  • Funnel and clean containers (for harvesting and storing)

  • Phytoplankton starter culture (e.g., Nannochloropsis, Tetraselmis, Isochrysis)

Supplies:

  • Saltwater (1.019–1.021 salinity, mixed with RO/DI or clean tap water and marine salt)

  • Fertilizer (Guillard's F/2 or similar phytoplankton fertilizer)

  • Bleach (for sanitizing your containers)

💡 Setup & Culturing Process

1. Sanitize Your Equipment

Clean your container and airline tubing with diluted bleach (around 1 part bleach to 10 parts water). Rinse thoroughly with tap or RO water. This helps prevent contamination from bacteria or algae.

2. Prepare Saltwater

  • Use reef salt mix with RO/DI or clean tap water.

  • Mix to a salinity of 1.019–1.021 using a refractometer or hydrometer.

  • Let it mix with a powerhead or air for 12–24 hours if possible.

3. Fill Your Container

  • Pour saltwater into the culture vessel, leaving a few inches of space at the top.

4. Add Fertilizer

  • Dose according to instructions (typically 1mL per liter for F/2).

  • Mix thoroughly.

5. Add Starter Culture

  • Add 10–25% of your container’s volume using a live starter culture (e.g., 250–500mL into 1 gallon).

  • Gently stir or shake to distribute evenly.

6. Add Aeration

  • Insert airline tubing directly into the bottom of the container—no airstone needed.

  • Turn on the air pump. Strong bubbling is ideal for keeping the phyto suspended and oxygenated.

7. Provide Light

  • Use a full-spectrum LED grow light or daylight fluorescent bulb.

  • Run light for 16 hours ON / 8 hours OFF using a timer.

  • Keep light close to the container, but avoid overheating.

8. Let It Grow

  • Your culture should darken over 5–10 days.

  • Keep the temperature 68–78°F (20–25°C) for best growth.

  • Avoid contamination—keep the top loosely covered and don’t introduce dirty tools.

🧼 Harvesting & Storage

When It’s Ready:

  • When the culture turns a dark green, it’s ready to harvest.

  • Turn off air for 30–60 minutes to let debris settle.

  • Carefully pour the top liquid into clean bottles using a funnel.

Storage:

  • Store in the refrigerator (34–40°F).

  • Shake daily to prevent settling.

  • Use within 3–4 weeks for best results.

🔁 Restarting the Culture

  • Always save a portion of your live culture to start the next batch.

  • Rinse your container with water and sanitize between batches.

  • Scale up easily by splitting into multiple bottles or buckets.

❗ Pro Tips

  • Cleanliness = success. Bleach between batches to avoid crashes.

  • Watch for signs of culture crash: bad smell, clarity, or clumping.

  • Don’t over-fertilize—it can lead to imbalance and contamination.

  • Label your cultures with dates!