Culturing Rotifers in Small Systems (Home or Lab)
Related Support Pages: Rotifer Enrichment Rotifer Feeding Rotifer Feed Calculator
Related Products: Live Rotifers RGcomplete Compact Culture System (CCS)
The Basic Setup
A 5 gallon (ca. 20 liter) bucket is a typical setup for a small system. They are inexpensive, easy to move around, and easy to clean. A 5 gallon bucket containing 4 gallons of water at 500 rotifers/ml (low density) will hold roughly 7.5 million rotifers and yield 2.5 million rotifers per day with a 33% daily harvest.
If you choose to set up a more sophisticated rotifer growing system, please check out our Instant Algae® Rotifer Recipe for Aquaculture.
- 3 to 5 gallon bucket or larger tank
- Rotifer Floss (waste trap)
- Dechlorinated salt water
- Temperature 25-28 °C/ 77-82 °F is best
- Salinity 10-35 ppt (Specific Gravity 1.0075 - 1.026), optimum 15-20 ppt
- Live rotifer culture
- Microalgae rotifer feed (we recommend RGcomplete®)
- Keep enough microalgae in the system so that the rotifers never go hungry
- Harvest at least 20-30% of your culture every day (more is better!)
Your rotifer culture system must be set up in a stand-alone tank - they cannot be raised in a reef tank or co-cultured with other organisms. Glass aquariums don't work as well as buckets. We recommend a very simple model consisting of nothing more than a bucket or tank with an air stone.
Starting your culture
- Put the bag of rotifers in the bucket to allow it to slowly warm up
- Wait 5 minutes then open the bag and add the rotifer starter culture
- If you are starting with 1 million rotifers, add 11 mL RGcomplete or other algae feed
- Add microalgae daily but wait at least 3 days before starting to harvest them if it is desired to build up the population as rapidly as possible
- Add enough RGcomplete to maintain a light green color between feedings. Typically this will be 11 ml daily per million rotifers for maximum production, less if you need fewer rotifers.
- Harvest at least 20-30% of your culture each day (more is better!)
Harvesting Your Rotifers to feed a Reef Tank
- Before harvesting your rotifers stir the culture vigorously for 10 seconds. This will lift the detritus from the bottom, keeping the culture clean and running continuously for many months. This will not damage the rotifers at all.
- Harvest 20-30% (more is better!) of your rotifer culture. This can be done by scooping with a jar, or pouring the culture out of your bucket.
- Turn off your skimmer but leave your pumps running (many people put their skimmers on vacation timers so they turn on again automatically).
- Pour your rotifers directly into your reef tank. The water become cloudy momentarily until the detritus settles to the bottom.
- Remove an equal amount of water from your reef tank. Pour it through a coffee filter back into your rotifer tank to replenish the water.
Harvesting Your Rotifers to feed Fish Larvae
- Turn off your airstone for 2-3 minutes. This will allow the detritus to settle and the rotifers will swim to the top (they swim toward light)
- Harvest as many rotifers as you need by gently scooping them off the top of your tank
- If you have a reef tank follow the instructions above
- If you don't have a reef tank you will periodically need to clean your culture tank to prevent the detritus levels from building up and generating ammonia. Use a modified version of the Reef Tank directions and either use or dispose of the rotifers
Since rotifers need to be maintained/harvested every day, it can be a problem if you go out town for several days. Fortunately there is an easy way to put your rotifers in "vacation mode" (hibernation):
- Pour a liter or so of your culture into a 1 liter container. Cover loosely to allow oxygen to enter.
- Add a bit of extra algae to darken the culture
- Put the liter container into your refrigerator
- After 7 days 50% of your rotifers should be alive
- After 14 days 15% of your rotifers should be alive
- Restart your culture using the directions above
- Rotifers do not need any light. They are phototrophic (attracted to light) but do not require it.
- Do NOT let the rotifers ever run out of food. The survivors will take up to 24 hours to recover and start producing again
- The rotifers are shipped to you at a salinity of 30 ppt. They can be gradually acclimated to range from 4 ppt to 45 ppt
- Rotifers will grow best at 1/2- 2/3 standard seawater salinity. However they grow fairly well at full salinity, and it is easiest to just use water from your existing system.
- Rotifers won't care if you use new water or water from your reef system. If you use water from your reef, pour it through a filter first to remove any zooplankton. A coffee filter is a very inexpensive filter that works well.
- Air must be bubbled through the culture. Rotifers have a very high metabolism and can quickly deplete the oxygen in the water. If excess foam accumulates on the water surface, reduce the airflow
- Rotifers will do best in a pH range from 7.0 to 8.0.
- It's difficult to measure your rotifer densities without a microscope, so it might take 2-3 weeks before you find, by experimentation, an equilibrium in your system for how much algae to feed and how many liters of rotifers to remove each day without affecting your culture densities.
- ClorAm-X® neutralizes toxic ammonia released by the rotifers as a normal waste product. Use of ClorAm-X dramatically increases the number of rotifers that can be cultured in a small volume without requiring large daily water changes. RGcomplete™ contains ammonia control so additional ClorAm-X is not needed.
- Rotifer Floss is a fibrous pad that you can hang in your culture to help keep it clean by accumulating solid wastes. Hang the floss in the culture like a curtain and weigh down the bottom so it doesn’t float. To clean it, simply rinse in a spray of tap water and put it back into the culture.
Rotifers fall into two salinity categories - marine and freshwater. “Marine” rotifers are actually brackish water in origin and can survive and grow in salinity ranging from 4 ppt to 40 ppt.
There is much more information about culture of marine species, and they are therefore the preferred choice. The drawback is that rotifers grown in 20-30 ppt salinity are shocked when put into fresh water. They are not killed, but they may stop swimming for a time until they adjust to the lower salinity. But there is an easy solution - grow the marine rotifers at a lower salinity (15 ppt is actually the optimum). At 5 ppt marine rotifers such as Brachionus plicatilis will grow well, although they won't be quite as prolific. When the 5 ppt rotifers are put in fresh water (0 ppt) they will stop reproducing but remain healthy, alive, and will maintain their enrichment levels (for at least 1 hour).
To cultivate 5 ppt rotifers it is best to drop the salinity gradually, preferably lowering it no more than 10 ppt per day if you want to maintain production. While you are lowering the salinity the egg count and reproductive rate will be reduced, but once the rotifers have been at the target salinity for 48 hours they should rebound quickly. Always make sure that the ammonia (NH3) level is kept low (preferably less than 0.5) to avoid stressing the animals.