Algae on Anubis

[Russ84]

Hello can anyone tell me what this algae on my anubis is and how to get rid of it. when ever a new leaf comes out within a month the algae spreads to it thanks
it is the dark almost black stuff on the edge of the leaves

 

[WyldFya]

Black beard algae. Excel is one method for removal, just use high dosages to get rid of it, or in extremely difficult cases a 19:1 water:bleach solution dip for 4 minutes will kill the algae.