Cat - I have seen very similar stuff like this before. It can have various colors. I think it is the late stage of one of the Cyanobacteria (blugreen algae). I have found a good thing enviornmentally safe thing to remove it when it is blown into a corner as you have it, is to use one of the peroxygen carbonate products such as Green Clean, Phycomycin or Pak 27. Another thing to use would be to spray the scum with Cutrine-Plus liquid.


aka Pond Doctor & Dr. Perca Read Pond Boss Magazine -
America's Journal of Pond Management