it is green hair algae , best way to get rid of it is lighten up on feedings , a lot of times this happens due to over feeding but not always , suck it out while doing large water changes , usually when this occurs your nitrates and phosphates are so high they will not even read in a test .
this can occur if your water changes are too small and not often enough,
sometimes this can also be because your water source may contain lots of phosphates
have you ever tested your water source ,
I prefer to battle this algae with out chemicals , just large water changes should do the trick ,
some use the vodka method ,
green hair algae