Paramecium caudatum

Aquarium keeping is an exciting hobby that allows us to delve into the underwater world and explore the diversity of aquatic life. Usually, we are accustomed to seeing colorful fish, various aquatic plants, shrimps, and snails. However, the aquarium is also home to numerous microscopic organisms that aquarium enthusiasts are often unaware of, but which can be surprisingly interesting. In this video, we will immerse ourselves in the world of the microscopic aquarium inhabitants and look at Paramecium caudatum.

Paramecium caudatum is one of the best known and studied unicellular microorganisms, it inhabits practically all freshwater bodies of our planet. Paramecium caudatum belongs to the class of Ciliata, which means that the entire body is covered in cilia that can rhythmically move, enabling locomotion and allowing the cell to direct food particles into the oral opening, called the cytostome.

Size & resemblance

In terms of size, it is not the largest representative of unicellular organisms, but it does not belong to the smallest either. Sizes range from 50 to 300 micrometers. The shape of these infusoria resembles a slipper: oval, with a distinct heel and toe, which is why this microorganism was used to be known as the slipper animalcule.


Reproduction of Paramecium caudatum occurs through binary fission, resulting in the formation of two identical individuals. However, since nature does not want the planet to be overrun by identical animal clones, many microorganisms have developed a method of sexual reproduction known as conjugation. Conjugation allows unicellular organisms to combine different genes, renew and exchange their genetic material, promoting genetic diversity within the population.


Paramecium caudatum possesses a high sensitivity to changes of the surrounding environment. It is capable of responding to factors such as light, temperature, and the chemical composition of water, which helped the microorganism adapt and survive in various conditions over millions of years.


Paramecium caudatum holds great significance for the healthy life of an aquarium. Together with other beneficial microorganisms, it participates in the decomposition and processing of leftover fish food and their metabolic byproducts. In the meantime it is a food source itself for baby fish and other animals. The slipper ciliate plays an important role in creating and maintaining the biological balance in the aquarium, allowing us to enjoy a healthy aquarium with crystal-clear water.


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