What is a rotifer?

It is a very small, organism used in aquaculture as a live food. Rotifers are invertebrates that are found in a variety of aquatic environments. Growing larval clownfish on rotifers is very common in aquaculture and highly recommended. While it is not the only thing to feed to clownfish larvae, it certainly is easier to propagate than many other live food options like copepods.

Do I need to culture rotifers?

We strongly recommend you culture rotifers if you wish to be successful. This animal is a great live feed organism for clownfish larvae. Rotifers can be grown in high-density cultures with the use of our feeds, techniques, and equipment. A good rotifer culture can be continuous, producing potentially millions of rotifers per day. When fed a proper diet, rotifers can be nutritionally valuable to clownfish larvae.


When you are ready to take on rotifer culture, here is a list of recommended products to get you up and running:

How do I culture rotifers?

With our live rotifers, food, equipment, and recommendations, you can culture rotifers continuously. Here are some simple steps for culturing:

  • Feed your rotifer culture at least 2 times a day with our RGcomplete.
  • For small-scale production, we recommend starting off with 6 mls of RGcomplete total, so 3 mls in the AM and 3 mls in the PM. You can build the feed amount over time if you need more rotifers.
  • For breeders with a high demand for rotifers, we recommend using a small dosing pump to feed out the algae multiple times a day. You can feed up to 30 mls of RGcomplete every day with this method. You do not need to keep the algae refrigerated if you refill the food reservoir every day from the bottle you keep in the fridge. Purging the feed lines with DI water is good to do every day to keep them clean. It is best to keep the dosing pump and feed reservoir close to the culture so that you can keep the feed lines short and minimize residence time of the food in the lines.
  • 5 gallon bucket is useful for rotifer culture.
  • Temperature range should be 75 – 80F.
  • No light required.
  • Ample aeration is recommended. You can use an open ended, rigid airline for this. No need to use a diffuser or air stone.
  • Daily observations are important. You can either use a microscope with up to 10X magnification to view your rotifers or simply dip a clear glass container in the culture and illuminate them with a flashlight from underneath the container. They have a very lazy swimming pattern.
  • We recommend at least a 25% harvest every day. This will help keep the water clean since it is a water change like you do on your tanks and it keeps the rotifer culture young and vigorous.

You can find additional information about culturing rotifers on the ROTIFER CULTURING SUPPORT page on the Reed Mariculture website.

What do I do with the extra rotifers if I do not have larval fish to feed?

You can feed the rotifers to your reef tank. Your fish and corals will gladly consume them. It is also possible to get them to populate a refugium if you are feeding phytoplankton daily. Our Phyto-Feast is great for keeping them happy. Many stores and hobbyists culture rotifers to feed to corals even if they are not breeding fish.

Can I store rotifers as back-ups?

Yes. We recommend you put some of your harvest (100,000) in 1 liter of saltwater in an open container in the fridge. Replace the stored rotifers once a week with freshly harvested ones. Make sure to add a few mls of RGcomplete or other algae to the container on the first day. No need to feed them again or stir the contents. We also recommend that you run at least 2 cultures in case one is crashing.

Can I put the rotifers with their culture water in the larval rearing tank?

No. We recommend that you separate the rotifers from the culture water with our Zooplankton Harvest Sieve. This device will capture all the rotifers.

How do I know if my culture is crashing?

Daily observation of your rotifers is vital. We strongly recommend the use of a microscope for counting and observation. If you do not have a scope, you can easily view the rotifers in a clear, glass container. Take a sample every day and use a flashlight to observe. Look for normal swimming behavior and density. If you see fewer rotifers in the sample, you may need to check water quality and take a day or two off from harvesting the rotifers. You can still perform a harvest but put the rotifers back. This will ensure that you have done a water change on the culture while retaining the rotifers. It is best to run at least 2 cultures in case one crashes. Having a reliable source of rotifers may be important if you are raising clownfish larvae.

How do I harvest my rotifers?

When harvesting from your culture, always make sure that you leave the air on so that the rotifers remain evenly dispersed. When the air is off, the rotifers tend to accumulate at the surface which will result in an over harvest. Over harvesting can cause the rotifer density to decline beyond the point of recovery. Using a cup or other harvesting container, remove a measured portion of the culture. Make sure you do not remove more than 20% on any given day. Pour the harvested rotifers through a sieve and discard the culture water. You can use our Zooplankton Harvest Sieve for this step. Rinse the rotifers out of the sieve into a container with clean, new saltwater. It is a good idea to observe the harvest with a flashlight to see if the rotifers are swimming and health. They tend swim in a slow, lazy manner. From here, you can discard the rotifers, feed them to your larvae or feed them to your corals, if you have them. Enriched rotifers are a great food source for corals and small-mouth fish.

Is it challenging to breed clownfish?

Yes, it can be quite challenging. We offer equipment, foods, live rotifers and weaning diets to make it easier. In our experience, mastery of rotifer culture is vital to your success. With consistent effort and attention to detail, you can be successful.

How do I get my clownfish to spawn?

Typically, 2 small, young clownfish will form an adult pair that will spawn for many years. They are male when they are young. When they begin to pair up, one of them will change sex and become a female. Tank water must be stable and clean. Feeding them with nutrient dense food throughout the day is ideal. We recommend our TDO Chroma BOOST pelleted food, Arcti-Pods and Mysis-Feast for all your broodstock nutrition.

How often should I feed my clownfish pair (broodstock)?

At least twice a day. We recommend feeding TDO Chroma BOOST (Small or Medium) at least twice a day.

You can use an auto-feeder to make it easier. We also recommend incorporating other food types into their diet. Simply feed small amounts and rotate food options. These foods that we make are a great addition to the diet:

  • Arcti-Pods: concentrated copepods
  • Mysis-Feast: concentrated mysis shrimp high in omega 3 fatty acids
  • R.O.E.: concentrated fish eggs rich in fats, proteins, and vitamins

How often do clownfish spawn and should I keep a log?

They typically spawn every 7-10 days. Once the pair begin spawning, start a log to track how often they lay they eggs and when the embryos hatch. Keeping track of when the eggs are laid and when they hatch allows you to remove the embryos 24 hours in advance of hatch to transfer to the larval rearing tank. We recommend that you allow a new pair to spawn 3 times before taking on larval rearing. They very often do not have well-developed eggs and fertilization can be low for the first two to three spawns.

How do I know when the eggs are about to hatch?

The eggs, which are orange or red in coloration, transition to an embryo. Embryos become brown, and you can see the eyes, clearly. The eyes become very shiny and silvery when the embryos are mature and ready to hatch.

My clownfish laid eggs on my reef rock. How do I collect them?

We recommend the Vossen Larval trap for collecting larvae. 

Will clownfish spawn on other surfaces?

Clownfish will spawn on a variety of surfaces. We recommend that you train them on to a floor tile or small, clay flowerpot. It is much easier to remove the embryos the day before they hatch this way. It can be tricky to train them to spawn on these types of items if the pair is in your reef tank.

What size tank is appropriate for a breeding pair?

If you are serious about breeding clownfish and want to house multiple pairs, we recommend keeping the pairs in separate tanks, this way you can manage their spawning habits and remove the embryos without disturbing the rocks and animals in a reef tank or community tank. Clownfish pairs do not need reef rock in an aquarium to spawn. They will also spawn just fine in a 10 gallon tank.

Does my clownfish pair need an anemone?

No. They do not even need structure beyond the floor tiles or pots you have in there for them to spawn on.

How do I hatch the embryos in a larval rearing tank?

The night before a hatch, remove the substrate where the embryos are attached. Transfer them to a larval rearing tank that has the same temperature and salinity as the broodstock tank. It is ok for them to be out of water for a minute or so. If there are things growing on the substrate like bacteria, algae or sponges, simply scrub them off being careful not to damage the embryos. Use aeration to keep the embryos clean and free of fungus before they hatch. You can use a bubble wand or air stone for this. Make sure the aeration is gentle and covers the entire nest.

Do I need a heater in the larval rearing tank?

Yes, unless you have a warm, climate-controlled room. They do best from 78° – 80°F

When do I add rotifers?

Add them after the fish hatch.

When do I add greenwater?

Add greenwater after the fish hatch.

What is “greenwater”?

Greenwater is a technique that involves adding algae (alive or dead) to a larval rearing tank for a few reasons as seen below. If you don’t want to grow live algae, we recommend our Rotigreen Omega.

Colonizes the digestive flora of the fish gut — marine fish are born with only a partially-developed intestinal tract, and it can take up to four weeks for the gut to fully develop. Our Instant Algae brand of microalgae and the associated “good” bacteria enter the gut and help jump-start digestion.

Enrichment of the rotifers — many hatcheries keep a background level of live rotifers in the tanks so the fish can continue feeding. Our greenwater microalgae feeds the rotifers and maintains enrichment levels.

Reduces or eliminates “nose bumping” syndrome — in larval tanks the water is typically so clean and clear that the fish lose depth perception and run into each other and the sides of the tank, bruising themselves and creating bacteria problems. Our Greenwater clouds the water and helps fish avoid collisions.

How do I store and use the greenwater food, RotiGreen Omega?

If the algae arrives frozen, put it in a refrigerator in a container for 24 hours to thaw. If it is thawed upon arrival, complete the following steps:

  • Pour the algae into ice cube trays.
  • Place the cubes into a freezer bag to prevent “burn”.
  • Thaw a cube in a sealed container in the refrigerator 24 hours in advance of using it.
  • Use the thawed portion within 3 weeks.
  • Note: The size of the cubes depends on how much you go through. No matter the size of the cube/portion, it needs to be used within 3 weeks to avoid spoilage.

How much greenwater do I use?

Use enough to cloud the water, but not very dark green. You basically want enough tint to keep the larvae swimming around the tank and not pinning themselves to the glass.

Feeding rotifers to your larvae

Clownfish larvae begin feeding on the day of hatch, so it is important to have live rotifers in the tank with them. We recommend 10 rotifers per ml as an initial stocking density. It is beneficial to feed your larvae a few times a day, but make sure not to overfeed the tank. If your rotifers get out of control in the tank, they can cause ammonia to spike and dissolved oxygen to drop. This can result in the death of your larvae. If rotifers get out of control, you can simply siphon water out of the tank to dilute them. Make sure to avoid siphoning out the larvae.

How do I keep the larval rearing tank clean?

It is advisable to do daily water changes to avoid high ammonia. You can use a rigid airline connected to a flexible airline to siphon waste off the bottom of the tank. Turn off the aeration during this step so you can see where you are siphoning so that you avoid sucking up the larvae.

What is weaning?

In fish culture the term weaning is used to describe the transition in the feeding of larvae, or juveniles, from live food to dry, or refrigerated diets.

How do I wean my fish off rotifers?

Weaning your fish off live rotifers makes growing your fish much easier. Once they are on to a dry food and other prepared food items, they grow quite rapidly and are easier to manage. Below is an example of a weaning schedule for the A. ocellaris or A. percula clownfish species. It is meant to be a visual guide to show how there is overlap when weaning. The key is to not switch from one food type to another, suddenly. This feeding chart does not necessarily apply to all species of clownfish. Our Hobbyist Breeder Pack is perfect for weaning your fish off live rotifers.

Do I need to hatch and feed baby brine shrimp when weaning?

If you are using TDO Chroma BOOST, there is no need to hatch brine shrimp every day. You can go from live rotifer to TDO which is much simpler.

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