How to Set Up a Rotifer Culture for Zebrafish Larvae

Rotifers (Brachionus plicatilis) are one of the most important live feeds for zebrafish (Danio rerio) larvae during early development. Their small size (~150-200 µm for L-type), high nutritional value, and ease of culture make them ideal for supplementing dry feeds like Gemma Micro during the critical 5-30 dpf window.

This guide walks you through setting up a continuous rotifer culture using the Compact Culture System (CCS) and RGcomplete microalgal feed — the standard approach used by hundreds of zebrafish facilities worldwide.

1. Understanding Rotifer Biology

L-type rotifers (B. plicatilis) are marine zooplankton that reproduce asexually under favorable conditions, doubling their population every 1-2 days. A well-maintained culture can produce millions of rotifers per week from a single 14-liter CCS bucket.

Key biological parameters for successful culture:

2. Setting Up the CCS

Equipment Assembly

The Compact Culture System consists of five components: the T-assembly support, rigid airline, airstone, floss carrier standpipe, and a pair of CCS clips. Assembly takes approximately 5 minutes.

1. Remove the airstone from the rigid airline by pulling it off gently.
2. Insert the rigid airline into the T-assembly support through the hole in the top of the T-fitting.
3. Attach the standpipe — insert the top of the floss carrier standpipe into the T-fitting.
4. Re-attach the airstone by carefully sliding it onto the end of the rigid airline.
5. Clip the assembly into the bucket — attach CCS clips to opposite sides of the bucket rim, then seat the T-assembly arms into the clips.

Initial Culture Setup

1. Prepare saltwater — mix marine salt to 15-20 ppt in 14 liters of dechlorinated water. Verify salinity with a refractometer.
2. Add saltwater to the CCS bucket and install the T-assembly.
3. Set temperature — place a submersible heater set to 27°C in the bucket or in the room.
4. Connect air supply — attach airline tubing from the air pump to the top of the rigid airline. Adjust flow to 1.5-2 LPM.
5. Add rotifer starter culture — inoculate with at least 1 million rotifers.
6. Add initial feed — dose 11 ml of RGcomplete per million rotifers in the bucket.

3. Daily Maintenance Protocol

A successful rotifer culture requires consistent daily maintenance. The entire process takes approximately 15-20 minutes per bucket.

Step 1: Harvest Culture & Water Change

Once the culture reaches your target density (typically 200-500 rotifers/ml), harvest 20-30% of the culture volume daily. Use a sieve (41 µm mesh) to concentrate the rotifers, then rinse with clean saltwater before feeding to zebrafish.

Step 2: Clean Rotifer Floss

Remove the T-assembly from the bucket, lift out of the water, and let free water drip back. Flush waste from the floss with a strong spray of clean water. The floss acts as a biological filter — keeping it clean is essential for water quality.

Step 3: Brush Bucket Surfaces

Use a dedicated brush to scrub the interior surfaces of the bucket, removing adhering detritus. This organic waste will be trapped by the floss during the next cycle.

Step 4: Replenish & Feed

Replace the harvested volume with fresh saltwater at the correct salinity and temperature. Re-install the T-assembly, add the daily dose of RGcomplete (11 ml per million rotifers to be harvested), re-attach the cover, and reconnect the air supply.

4. Counting Rotifers

Accurate counting is essential for maintaining consistent feed rates and harvest volumes. Here's the standard counting protocol:

1. Stir the culture thoroughly to ensure a representative sample.
2. Pipet a sample (typically 1 ml) into a vial. Add 2-3 drops of vinegar to immobilize the rotifers.
3. Transfer to a counting slide — use a Sedgewick-Rafter chamber (50 × 20 = 1,000 squares) for the most accurate results.
4. Count under a microscope — count at least 100 rotifers for statistical reliability. Multiply by the appropriate factor to calculate rotifers per ml.
5. Calculate total culture density — multiply rotifers/ml by total culture volume (typically 14,000 ml for a CCS bucket).

5. Nutritional Enrichment

RGcomplete already provides high levels of DHA (41.9 mg/g), EPA (18.1 mg/g), and ARA (2.1 mg/g) — sufficient for many zebrafish protocols. However, for species with higher fatty acid requirements, a secondary enrichment step can be added using N-Rich PL Plus (phospholipid-rich) or N-Rich High PRO (protein-rich).

The typical enrichment protocol involves a 2-8 hour incubation with N-Rich products before harvesting the rotifers for feeding. This raises DHA levels from 17 to 36-40 mg/g dry weight, approaching the fatty acid profile of wild-caught prey items.

6. Troubleshooting Common Issues

7. Scaling Up Production

For facilities requiring large volumes of rotifers (>10 million/day), multiple CCS buckets can be run in parallel, or you can transition to a larger zooplankton reactor system. Planktovie offers consultation services for designing and optimizing rotifer production systems at any scale.

For facilities that prefer to purchase rotifers directly rather than culturing them in-house, Planktovie supplies QM Diagnostics-certified L-type rotifers in quantities from 1 million to 100 million, shipped under temperature-controlled conditions.

Products Used in This Protocol