ae have been used in animal and human diets since very early times. Filamentous algae are usually considered as 'macrophytes' since they often form floating masses that can be easily harvested,although many consist of microscopic, individual filaments of algal cells. Algae also form a component of periphyton ,which not only only provides natural food for fish and other aquatic animals but is actively promoted by fishers and aquaculturists as a means of increasing productivity. This topic is not dealt with in this section,since periphyton is not solely comprised of algae and certainly cannot be regarded as macroalgae .However,some ancillary information on this topic is provided in Annex 2 to assist with further reading . Marine'seaweeds' are macro-algea that have defined and characteristic structures.