Black Algae

[The Duke]

Hi. I have a 190 little juwel trigon. Been set up about a year and stats as of yesterday were ammonia and nitrite zero and nitrate 5 ppm. The tank is suffering with what looks like a form of black algae, I have amazon sword in there and the leaves are turning black. The lights are on for 7 hours a day. I would probably say I am at the limit fish stock wise but nothing major. Weekly 50% water changes. Any advice on how to get rid of this horrible looking algae?

 

[Chtheo]

Hi,

Not really sure what algae it might be, can you either describe it more or supply a picture?

alternativley i have found this guide brilliant in ID-ing and dealing with algae Algae Guide