Rotifer and Copepod Culture Guide: How to Culture Initial Food for Marine Fish Fry at Home | ブリちょく
Marine Fish| ✍️ BreederDirect Editorial
Rotifer and Copepod Culture Guide: How to Culture Initial Food for Marine Fish Fry at Home
This guide explains how to culture rotifers (Brachionus) and copepods at home, which are essential for raising marine fish fry. We cover everything from preparing culture containers, seawater, and phytoplankton to maintenance management and feeding timing.
Key Takeaways
This guide explains how to culture rotifers (Brachionus) and copepods at home, which are essential for raising marine fish fry. We cover everything from preparing culture containers, seawater, and phytoplankton to maintenance management and feeding timing.
Why Live Food is Essential for Marine Fish Fry
When attempting to breed marine fish, the first hurdle you'll face is the problem that fry won't eat anything. Many marine fish fry, such as clownfish, gobies, and seahorses, can only eat minute live food with the ability to swim from immediately after hatching.
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Even if frozen food or artificial pellets enter the fry's mouth, they spit them out. While commercially available brine shrimp nauplii can be used, they are often too large for newly hatched fry and are particularly unsuitable for small species.
The solution to this problem is rotifers (Rotifer) and copepods (Copepoda). These are types of marine plankton and are used by aquariums and breeders worldwide as live food of a size suitable for fry mouths. This article provides a practical guide to culturing them at home.
Culturing Rotifers (Brachionus)
What Are Rotifers?
Rotifers (Rotifer in English) are minute zooplankton measuring approximately 100-300 μm in length. The most widely used species is Brachionus plicatilis (brackish water to marine-adapted), which can be cultured in seawater with a specific gravity of approximately 1.018-1.022.
What You Need
Culture containers: Clear plastic bottles (2L) or acrylic cylinders (5-20L)
Aeration: A gentle air stone and thin silicone tubing
Seawater: Specific gravity 1.018-1.020 (artificial seawater is fine)
Rotifer cultures: Available from specialty shops and online retailers as "rotifer culture kits"
Phytoplankton: Rotifer food (Nannochloropsis is the most readily available)
B-complex vitamins (optional): Used for DHA/EPA enrichment
Culture Procedure
1. Preparing the Culture Water
Adjust artificial seawater to a specific gravity of 1.018-1.020. The ideal temperature is 25-28°C. Remove chlorine from tap water by aerating for 24 hours or neutralize with sodium thiosulfate.
2. Introducing Seed Rotifers
Add purchased rotifers to the culture seawater. An initial density of 100-300 individuals per mL is recommended.
3. Feeding Phytoplankton
Add commercial Nannochloropsis solution 1-2 times daily until the culture water is a light green color. Be careful not to overfeed, as this can foul the water and cause culture collapse.
4. Daily Management
Run aeration continuously (low to moderate)
Feed once per day
Perform 50% water changes every 3-5 days (discard old water, replace with fresh culture water)
5. Harvesting
Five to seven days after inoculation, rotifers can be harvested when density increases. When the water becomes visibly cloudy white (500-1,000+ individuals per mL), they can be added to the fry tank.
The Importance of Density Management
Rotifers can experience "density shock" and collapse when density becomes too high. When density becomes very high, you must increase harvest volume or expand culture volume. Since re-culturing takes several days after collapse, we strongly recommend managing multiple culture containers on a staggered schedule.
DHA/EPA Enrichment
To enhance fry growth and health, enrich rotifers with DHA/EPA-containing nutrients before feeding them to fry. Add commercial "rotifer enrichment products" (such as Selco or CleanGreen series) 1-2 hours before feeding, allowing rotifers to absorb the nutrients before harvesting.
Culturing Copepods
What Are Copepods?
Copepods are small crustaceans measuring 500 μm to 2 mm in length. While adults are larger than rotifers, nauplii (250-400 μm) are an important food source for many marine fish fry. They are highly nutritious and rich in DHA, EPA, and astaxanthin, contributing to improved fry survival rates and coloration.
Commonly used species:
Tisbe biminiensis: Benthic type, fast reproducing and easy to breed naturally in refugiums
Tigriopus californicus: Hardy species, tolerant of high salinity and low oxygen
Acartia tonsa: Planktonic type, easy for fry to eat but somewhat difficult to culture
Culture Method
Basic Setup
Copepods are easier to handle than rotifers. They can be cultured by simply filling a 10-40L tank (no lid needed) with seawater and applying gentle aeration. A specific gravity of 1.020-1.025 is appropriate.
Feeding Method
Add phytoplankton (Nannochloropsis or Isochrysis) about 3 times per week. Benthic Tisbe also consumes detritus, so they will thrive stably even with just a small amount of organic matter (such as powdered spirulina) added once per week.
Harvesting and Feeding
One to two weeks after starting the culture, copepods will accumulate in large numbers on the tank walls and bottom. At this point, use a dropper or silicone tubing to siphon them out and add them directly to the fry tank.
By culturing Tisbe in a refugium (a separate chamber connected to the main tank), copepods naturally flow into the fry tank, creating an environment where copepods are available constantly.
Using Rotifers and Copepods Appropriately
Fry Size/Age
Recommended Live Food
Just after hatching - 3 days (smallest mouth size)
Rotifers only
4-14 days
Rotifers + Copepod nauplii
14+ days
Rotifers + Adult copepods + Brine shrimp nauplii
1 month onwards
Transition to copepods + brine shrimp + artificial food
Clownfish and goby fry typically begin eating rotifers immediately after hatching. They can transition to brine shrimp in about 2 weeks.
Key Points to Prevent Culture Failure
Signs of Culture Collapse
Foam accumulates on the water surface and the water smells bad
Tank walls turn brown
Rotifers/copepods suddenly disappear
To prevent collapse, thorough water changes and attention to overcrowding are essential. If density becomes too high, increase harvest volume and maintain optimal density to prevent collapse.
Managing Multiple Containers in Parallel
To ensure stable supply as a breeder, manage 2-3 rotifer culture containers on a staggered schedule (3 days apart). This allows you to diversify risk so supply won't stop if one culture collapses.
Summary—Live Food Culture is a Fundamental Breeder Skill
Culturing rotifers and copepods is an essential skill for breeders who reproduce and sell marine fish. While it may feel difficult at first, once you get the hang of it, you can maintain stable cultures.
If you want to dramatically improve fry survival rates, start by culturing rotifers first. On "br-choku," many breeders offer bred specimens, and you can ask them directly about culture tips when purchasing. Please take advantage of knowledge sharing between breeders.
