Culture of fish food organisms

Unit 5 - Infusorians

5.1.Introduction to Infusorians
These "animalcules" were first described by Antony Van Leeuwenhoek in his Philosophical Transactions of 1677. The term "infusoria" comes from the practice of steeping substances (usually hay) in water by soaking at temperatures less than the boiling point. Only the largest of the protozoans (infusoria) are large enough to be seen by the naked eye. Most species require a microscope to view. The "green water" or cloudiness of aquarium water is sometimes an indication of an overabundance of infusoria which can be caused by overfeeding. The importance of infusoria to the pisciculturists is with their use as fry food. Their small size, ranging from 25 µm to 300 µm makes them an ideal live food for young fry which have just consumed their yolk sac. This includes ciliates and protozoan’s. They obtain holozoic nutrition from bacteria, algae and detritus. They reproduce by binary fission or conjugation. Freshwater species includes Paramecium and Stylonichia and marine water species includes Euplotes (20-35 ppt).