FishTal Propagations

Culturing Live Rotifers

Live rotifers are the most common "first food" for larval fishes.  Unfortunately, rotifers are only nutritious if they are fed nutritious food.  First we will deal with culturing protocols and then move on to enrichment.

Things you'll need:

• 5 Gallon buckets
• Flexible airline tubing
• Rigid airline tubing
• Air pump
• Rotifer starter culture
• Food (RotiGrow Plus, Instant Algae, live Phytoplankton, etc.)
• 60CC Syringe (Available at your local pharmacy.)
• 120 micron strainer
• 53 micron strainer

First, a little info on rotifers before I get into the specifics of technique.

• Rotifers hatch in 12hrs and are sexually mature at 18hrs
• Female lifespan at 25degC is 6-8days (males only 2days.)
• Largely classified as into two strains L & S strain (B. plicatillis & rotundiformis respectively.)
• Brachionus Plicatillis is the most common
• Best growth occurs at salinity between 1.007-1.014
• Abrupt salinity change of 1.007 or more will cause mortality
• Optimum temp is 18-25degC  (Room temp in the fish room works well for me.)
• pH should be between 6.5-8.0
• Free Ammonia below 1mg/l
• For larval feeding suggest feeding nannochloropsis with 20% tetraselmis for optimal HUFA content. "Rotifer Diet HD" from Reed Mariculture is what I use.
• Rotifers do not need light to grow

Culturing Method

There are many ways to raise rotifers, the following is how I do it. 

Step 1)  Obtain a starter culture from a local source if possible.  Starter cultures are available online as well:  http://www.mariculturetechnology.com/Foods.htm 

Step 2)  Place the starter culture in a 5 gallon bucket. Add enough fresh saltwater with a specific gravity of 1.015 to double the water volume in the bucket. Feed with IA using the recipe below.

Step 3)  Insert a rigid airline tube connected to an air pump to provide aeration.

Step 4)  On day 2, add enough saltwater to double the volume again.  Increase the water volume again on the next day.

I find that maintaining about 4 gallons of water volume in a 5 gallon bucket works well.

Rotifer feeding protocols when using IA Rotifer Diet:

Dilute concentrated IA by adding 50ml to a 2L bottle and filling with fresh SW at 1.015SG.

Feed 10ml per gallon of culture size, twice a day.  ie; if you have a 4 gallon culture, add 40ml of the diluted concentrate twice a day. 

You NEVER want to allow the rotifer culture to become completely clear. It is absolutely necessary to keep the rotifers fed constantly to obtain a dense culture. Without a dense culture, you may wake up one day and find that there is no more food left for your fry.  Feeding smaller amounts, more frequently, is optimal.

Rotifers should be harvested every few days by using the 120 and 53 micron sieves.  The 120 micron sieve will strain out the larger particles and the 53 micron sieve will collect the rotifers:

After a few days you will notice a build up of detritus on the bottom of the bucket. This should be removed either by direct siphoning or stirring the culture before straining it.

UPDATE:

As of November 2010, I am now using RotiGrow Plus from Reed Mariculture for culturing my rotifers. I am diluting it in the same manner that I was diluting the Rotifer Diet except I am using freshwater for the dilution. I am also adding 5ml of Cloram X daily. I'm seeing increased production and cleaner culture vessels. I highly recommend using this product.

Also, of note, I no longer need to enrich my rotifers before using them.

Harvesting: 

Using a water pitcher I remove culture water and pour it through the sieves and back into the culture vessel.

Refreshing:  Following the procedure above, 50% of the water is drained into a waste bucket instead of into the culture vessel and replaced with fresh salt water.

This information is a summary of what I've learned from my own experience as well as knowledge obtained from reading "Plankton Culture Manual - Frank Hoff" and "Breeder's Guide - M. Wittenrich".  (See "Further Reading)

Enrichment

After rotifers are harvested they need to be enriched before using them as food for the larval fish.  Highly unsaturated fatty acids (HUFA's) are of prime importance to the survival of marine fish larvae.  Since rotifers themselves offer little nutritional value on their own they need to be enriched with HUFA's. The fatty acids, EPA and DHA, are the most important, with DHA the most essential. 

After harvesting, back-flush the 53 micron sieve with clean water using a turkey baster. I usually do this into a small plastic food container. After you have all the rotifers in the container add the enrichment and allow them to feed for 8-12 hours, depending on the instructions from the manufacturer. The specific type of enrichment you use will depend on the needs of the type of larvae you're working with.

Once the rotifers are enriched they should be rinsed with clean tank water before being added to the larval tank.

Update: As mentioned above, I no longer need to enrich my rotifers for use with most species. N-Rich from Reed Mariculture can be used as a seconday enrichment if desired.

A few notes about RotiGrow Plus

RotiGrow Plus Offers:

• Healthy Rotifer Cultures - Rapid growth, minimal fouling and reduced bacterial loads

• Higher Yields- Rotifers can double daily at densities over 5,000 L-type rotifers per ml

• Essential Omega Boost - Provides 50-100 percent of the Omega-3 fatty acids needed by the larvae of most marine species - without secondary enrichment!

• Optimum Enrichment - Supports full highly-unsaturated fatty acid (HUFA), full vitamin enrichment with proper protocols, and additional carotenoid enrichment of rotifers without sacrificing other nutritional factors or stressing the rotifers.

• Concentrated, Clean, Liquid Form - Exceptionally clean and easy to use with minimal foaming or clumping, which means less time spent maintaining cultures

Live rotifers: