Staghorn algae is a type of red algae that forms coarse long strands of gray green to solid green color. Sometimes it is almost white colored. It is very unsightly. It grows on the edges of plant leaves as well as on the edges of almost any hard surface. Composed of coarse strands or tufts, it grows in dense patches. It is very similar to black beard algae.
It sometimes forms long strands six inches or more in length which wave in the current. It is soft, slippery, and grows rapidly, yet clings tenaciously to plants and cannot be easily removed by hand. It generally comes with high nitrates or high iron.
Note that the green staghorn algae above is somewhat similar in appearance to a common water plant called Java Moss. Newbies often confuse the two.
Here is a link to an article on controlling all different types of algae including staghorn algae:
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