Infusoria

Infusoria is a word used to describe various freshwater microorganisms, including ciliates, copepods, euglenoids, planktonic crustaceans, protozoa, unicellular algae and small invertebrates.

In modern, formal classifications, the term is considered obsolete; the microorganisms previously and colloquially referred to as Infusoria are mostly assigned to the kingdom Protista.

Still, some advanced aquarists, with especially large collections of fish, will breed and cultivate their own supplies of the microorganisms.

[2] Infusoria can be cultured at-home by soaking any decomposing vegetative matter, such as papaya or cucumber peels, in a jar of aged (i.e., chlorine-free) water, preferably from an existing aquarium setup.

At this point, the infusoria are usually visible to the naked eye as small, white motile specks.