The horizontal flagellum allows the dinoflagelate to spin also. The one on the left is Ornithocercus magnificus , and the one on the right is Amphidinium cryophilum . This image shows the brown masses of dynoflagelates. The dark coloration of the rockwork in this image is due to large amounts of dynoflagelates. The term filamentous refers to having the appearance of a strand, or being stringy.
Filamentous algae are also micro algae.
Certain members of the Chlorophyta, Cyanophyta, and Phaeophyta fall under this catagory. This type of algae tends to plague aquariums that are near the middle or end of cycling. It may also pop up if something goes wrong in the aquarium and there are large amounts of nitrates being produced for an extended period of time. Once an aquarium has finished cycling, this type of algae tends to become extreemly unnoticeable, or even dissapear altogether. But like most things, this is just a tendency, and not a rule.