rotifer Rotifers are small (50-1000 µm) zooplankton that occur in freshwater, brackish, and marine environments. Rotifers feed on microalgae and are consumed by a wide variety of fish, shellfish, corals, and other organisms. They are used extensively in aquaculture and aquariums because of their very high reproductive rates (as great as doubling or better every 24 hours), ease of culturing, optimal size for larval fish, and nutritional profile that can be tailored to the needs of prey species by use of special feeds (see Rotifer Production and Enrichment).

 

Rotifer Feed Calculator

This calculator will help you to determine how much feed your culture requires to produce the number of L-type rotifers you need to harvest each day. These feed rates will produce the same biomass (food value) of S rotifers, but the rotifer numbers will be about 2.5 times higher.

The traditional technique for growing and harvesting rotifers has been to count the rotifers and feed the culture based on the count.  We recommend a very different technique–maintaining a constant harvest rate and regulating the growth of the rotifer population by regulating the amount of food you give them.  This results in more stable and predictable rotifer production.

Rotifer egg production is high for only the first 3–5 days of their 7–15 day (depending on temperature) lifespan, so for the best production it is important to harvest at least 25% of your culture each day to keep your population young and reproducing vigorously.  In a healthy culture the numbers of rotifers produced each day directly corresponds to the amount of feed you provide.  If you need more rotifers, keep the same harvest rate and simply feed more to your culture each day; feed less if you need fewer rotifers.  When you increase or decrease the feed it will take 1-3 days (depending on the magnitude of the change in feed rate) for the culture to reach a new equilibrium and stabilize production.

How many rotifers do you need to harvest each day? million
How big is your tank? liters
What is your daily harvest rate? percent

 

Number of rotifers needed in the tank million
Rotifer density per ml
 
Amount of Nanno 3600 OR Rotifer Diet to feed daily ml per day
Amount of ClorAm-X to add daily grams
OR
Amount of Rotigrow Nanno to feed daily ml per day
Amount of ClorAm-X to add daily grams
OR
Amount of RotiGrow Plus to feed daily ml per day
Amount of ClorAm-X to add daily grams
OR
Amount of RGComplete to feed daily ml per day
Amount of ClorAm-X to add daily grams

Note: Normally no ClorAm-X will be required when feeding RGcomplete, which contains ClorAm-X. With all feeds, actual ClorAm-X demand will depend on temperature as well as other factors. These recommended dosings will be adequate in most situations, but we recommend daily ammonia testing at least until a culture routine is established that maintains consistently low ammonia levels. Always use a salicylate-based ammonia test (turns green-blue) when using ClorAm-X.

Culturing Marine Rotifers for Freshwater Applications

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.

 

Rotifers for Zebrafish Larviculture