http://forum.aqua-fish.net/ A forum devoted to aquarium fish, plants, techniques and fish keeping as a whole. en http://forum.aqua-fish.net/?topic=what-is-algae#1 Algae is basically a form of basic plant life.It requires light to grow by means of the chlorophyll it contains as well as feeding of phosphates,nitrates in the water.They can be single celled,multi-celled ,filamentous, some of the macro algae can even have leaf like growth. Diatom algea are brown in colour ,they are composed of a single cell which is created with a silica wall for protection. Blue Algae can in fact be blue,black or brown in colour and can feel extremely slimy to the touch. Green Algae is the most common found in aquariums ,it can be a green powdery algae or in some cases green hair algae which is a nuisance to everyone. The most common cause of algal growth in the aquarium is lighting left on for too many hours or high phosphates,nitrates in the water. mickey 2008-05-08