Rotifers (Fry Food)

Quick Links:

• Intro
• Obtaining a Culture
• Culturing
• Harvesting

Trouble Finding Something Aquarium Related?
Try my Google custom Search.

You're probably reading this because A) Your Clownfish Spawned, B) Your Reidi or Kuda Seahorses Spawned, C) Something else spawned and now you are panicked and are scouring the internet trying to do your research real quick. Well.. hopefully you have come to the right place.

Intro

Rotifers are the mainstay of marine aquaculture. Like vinegar eels in FW aquaculture, they may be used very successfully as first foods of fry that are too small to consume BBS. Clown & Seahorse breeders know how notoriously small their fry can be and the importance of having a rotifer culture on hand.

Besides being used extensively for breeding, they are used very often for reef maintainance SPS Coral, Clams and other filter feeders love to "eat" rotifers as they are small enough to succumb quickly to coral stings and small enough to be easily trapped by zooplankton feeders. They are easily enriched with selcon or phytoplankton and easily transfer these nutrients to whatever may eventually eat them. The best thing is, they are feed and forget foods. They'll survive for a time in saltwater until eaten or filtered out by your mechanical filter. This sure beats feeding the "dead" stuff that you get at the LFS, which fouls the water the very second you add it to the aquarium.

Fortunately rotifers are easily cultured with (somewhat) minimal effort and require little space.

Here's a shot of my rotifer shelf under my seahorse fry tank:

[Back to Top]

Obtaining a Culture

Thanks to the increasing number of hobbyists that are actively breeding marine fish, many have rotifers readily on hand. Cultures are readily available online from aquaculture stores and even on E-bay. Personally, I have ordered rotifer cultures online and I would say that you should try to obtain some locally first and only if you can't then by all means go online and order some. The reasons are multifold.

• Online orders are comparative expensive. If you belong to a local aquarium club or know fellow breeders where you live, chances are they have a surplus of rotifers and you might be able to obtain a culture for free. Post a want ad on your local aquarium forum and someone may let you have some.

• Online orders usually ship by priority mail which takes 2 or 3 days to arrive. Even if they do arrive on time, there is bound to be some dead loss. Some shippers add live phyto into the the bottle for the rotifers to eat during their journey but also leave little room in the bottle for air. Guess what ... live phyto (i.e. plants) + darkness = CO2! Resulting in much of the rotifers suffocating to death. As a result, the culture arrives rather stinky and with only a fraction of the rotifers still hanging on to life. The culture will take hold, but it takes a little longer than if you can get a healthy culture to start with. Sure you can pay more for express overnight shipping... but is the extra $10 worth it for a $4 culture of rotifers?

If you really need to order online, then check out E-bay. Buy only from reputable sellers.

[Back to Top]

Culturing

Rotifer cultures are relatively undemanding. Give them the right water and right food, and they'll explode in no time.
Here's what you need:

• Culture Vessel. I use plastic rubbermaid jars which are exactly the same as my phytoplankton culture jars.

• Rigid & Flexible Airline Tube. (Same setup as if culturing phytoplankton).

• Aquarium Salt

• Aged tapwater (no need to use R/O. Its going to be poured away anyway).

• Food (live / frozen phytoplankton).

You can culture rotifers in really any jar or vessel. It doesn't need light nor does it need to be clear. But clear jars are useful because they help us to see gunk buildup and prevent from decanting the gunk into the rotifer sieve when harvesting. Also, if possible, make sure that the jars have a wide opening for easy cleaning. (Try cleaning the inside of a 2L soda bottle). My rotifer jars are set up exactly the same as my phytoplankton jars. The only difference is that lighting is not necessary for rotifer culture.

Mix up some saltwater to a S.G. of 1.015 - 1.017. Sure you can culture them at full strength seawater at 1.022 - 1.024, but i find that the culture is most productive at lower S.Gs. 1.015 - 1.017 seem to give me the best results.

Rotifers, like any other marine creature, need to be slowly acclimated to your water. If the S.G. difference between your saltwater and the water which the rotifers arrived in, osmotic shock may set in and cause your rotifers to either shrivel up or explode! Hence it is important to acclimate them carefully. Pour the culture out of the little bottles into you culture jar. Every 15 min or so, add a little bit of newly mixed saltwater to the jar until it is full. This should be gradual enough so as not to kill your entire culture.

By far the best thing to feed them is live cultured phytoplankton such as nannochloropsis. Simply follow the harvesting (feeding) instructions below. If you don't culture your own phytoplankton, then the next best thing would be to buy the frozen stuff. This is a concentrated paste of phytoplankton which can be stored short term chilled in the refrigerator or in the freezer (recommended) for long term storage.

I find that to get the best results with storage & feeding, what i do when i receive a bottle is to shake it vigorously in order to get all the phyto into suspension. Then pour the concentrated suspension into ice molds which you can then freeze. The best mold that i found so far is non other than the little plastic trays which comes with your frozen mysis / daphnia / bloodworms etc. These make for perfectly pre-portioned cubes which prevent the phyto from being freezer burned. Pour the phyto suspension into the mold and freeze. Now whenever you need to feed the rotifers, simply pop out a frozen cube and toss it into the culture jar. Easy Peasy. Feed enough to turn the water slightly opaque green.

A good way of determining when to feed / harvest cultures is by looking at the clarity of the water. The 2 jars on the right are starting to become clear as the rotifers have eaten the phyto. These are next in line for harvest. The 2 on the left has just been harvested and replenished with fresh phytoplankton.

Stay away from the store bought phytoplankton that you find on the shelf of your big box pet store. These are way too watered down to be much effective in culturing a good number of rotifers. Not to mention they cost much more than even frozen phyto.

[Back to Top]

Harvesting

There are a couple of harvesting techniques out there, but I like this one because it doubles up as my water change regime also. You will need a rotifer sieve.

I don't have any actual pictures of the process, but hopefully these illustrations will suffice.

[Back to Top]

Plug

[Back to Top]