Description: Forms a slimy mat of green goop for lack of a better term. Usually greenish despite name, but can be darker as it appears in this picture.
Removal: This stuff is difficult to get rid of, but can be done if you persevere. Capable of surviving in low to zero light and without nitrates, it only needs phosphates in your tank to feed off of. You can prevent it by utilizing mangroves and macroalgae that will reduce the phosphates in your tank and prevent it from forming. If you have a break out and are trying to deal with an established problem, then you should consider adding a chemical phosphate removal system to kill it. The setup, (you need a phosban reactor and a filter media), may run you up to $75, before tubing and getting your tank setup going. Increase flow to dead spots.
Fun Fact: Scientists believe Blue Green Cyano was one of the first life forms on our planet.