Rotifers

Currently we culture the rotifer species Brachionus plicatilis.  Rotifers present different challenges than phytoplankton or copepods.  This is a summary of our successes and failures attempting to culture zooplankton.

To Start

First we started with a commercial culture of rotifers.  A live culture of thriving rotifers is much easier to deal with than rotifer cysts. 

Culturing

             Specific gravity is a very important factor in culturing rotifers to a workable density.  A specific gravity between 1.007 1.014 is optimum.  Depending on what you plan to do with your rotifers should determine what specific gravity you should culture them at.

 

The first thing to remember is that rotifers are animals, and tend to be more sensitive to condition changes than phytoplankton.  According to Joyce Wilkerson in her book titled Clownfishes, she states that a change in specific gravity of .007 will cause rotifers to go into osmotic shock, causing them to turn white and fall to the bottom.  - try to avoid this, we learned the hard way!

             After a starter culture has been obtained, match a batch of seawater to the exact  specific gravity.  Your batch should match  the same volume of rotifers you have.  For example, if you have 300 ml of rotifers, make a 300ml batch of fresh saltwater.  The reason for doing this is to experience maximum growth rates.  It’s a matter of finding mates.  Throw 2 rotifers into a 10 gallon tank you may get nothing.  Throw 2 rotifers in 10ml of water and odds are they will find each other.  Again, this is based on our own observations.  

             So after you mix a batch of saltwater to match your batch of starter rotifers you will need a food source.  We use our own phytoplankton (nanno. sp.) for culturing rotifers.  We have found that fresh phytoplankton works much better than purchased varieties; not to mention it is much cheaper!  Always add phytoplankton to rotifers, not rotifers to phytoplankton.   The reason is the pH differences may kill the rotifers.  Rotifers tend to have a more acidic water and phytoplankton tends to have a higher pH.   The imbalances are due to an abundance, or lack of O₂ or Co₂.   Remember rotifers are animals and use oxygen, releasing carbon dioxide which can create low levels of carbonic acid (like a calcium reactor).

             After you have added enough phytoplankton to tint the water green, we add an airline tubing with a valve to bubble once every two seconds or so.   This is where it becomes a little subjective for us- we eyeball the culture and as soon as the water clears up some, we double the water again and add more phytoplankton.

             Once an active culture has been established and you feel you’ve gotten the hang of it we suggest putting a 20 oz bottle, with a small quantity of rotifers and phytoplankton into the refrigerator as a “backup”.   This is in case a culture crashes and all is lost.  You will need a 53 micrometer sieve to strain out the tiny rotifers; this can be obtained at many aquaculture supply stores.

Application

             Our initial reason for growing rotifers was to use them for breeding clownfish.  For this, a maximum density is needed.  Batch culturing, which is starting from scratch each time is the preferred method.  This gives you the maximum amount of rotifers possible for the vessel size you are trying to culture them in.

             If you plan to use rotifers to feed to corals, often times a continuous culture is best where a larger vessel (10 gallon tank) is set up and rotifers are harvested out every few days and fed to a tank.  One thing to remember is, your tank water is going to be at a higher specific gravity than your rotifer culture.  We suggest either growing rotifers at a higher specific gravity, or gradually acclimating them to your tank.