All green algae are microscopic but some forms organize themselves into visible colonies. Each cell of the colony has two flagella and an eyespot. The eyespot detects light and helps the colony stay in sunlight. The whole sphere rotates and rolls through the water. Sometimes the sheets or looser nets curl into cylinder shapes.
Some desmids also join end to end to make filaments in the water.
They join end to end to make long filaments or strands that are attached to rocks, sticks and shells. These filaments can branch out. This is a common form of green algae in aquariums. They also join to make long, branching filaments. The filaments can be attached to rocks, sticks and shells, or they can float freely on the surface of the water in tangled mats.