Cladophora aegagropila

Cladophora aegagropila (Moss Ball) is not really a plant, but a ball of algae, so it is a decorative exception from the rule about avoiding algae at all costs. It is normally found in shallow lakes, where the movement of the waves forms it into a sphere. In an aquarium it must be turned regularly to keep it in shape. C. aegagropila can be divided into smaller pieces, which become spherical with time, or which form a carpet, if attached to roots and stones. Protected in parts of Japan.
Height; 3-10cm Width; 3-10cm Light; very low-high Temp; 5-28'C
pH; 6-8.5 Growth; very slow Demands; Easy

Text from Tropica
Photo by Dusko Bojic