The Cladophora aegagropila is not really a plant, but a ball of algae measuring 3-10 cm in diameter. It is decorative but also helps prevent algae growth. It is found in shallow lakes, where wave action forms it into a sphere.

In an aquarium, it should be turned regularly to maintain its shape. The Cladophora aegagropila can be divided into smaller pieces, which become spherical over time, or it can form a mat if tied to roots and stones.

It is protected in certain areas of Japan.