Lots of Algae in the Pond
First, my apologies. Pond management questions that come to eXtension default to me in spite of my presence and professional activity being in the state of Ohio alone. If we come to discuss pesticides, please do also discuss relevant state law with your local Extension or Soil and Water Office or the relevant management agency.
I can't make out enough detail from your image, but the pond looks to be completely covered, likely by (1) some duckweed species or (2) a cyanobacterium or blue-green algae. Can you get better detail in an extreme closeup photo? If you pinch a bit of that color between your fingers, do you feel a solid texture (a cottony mat, very fine leaves, or even a graininess like corn meal), or does it simply feel like water?