when i worked at a hardware store about a year ago we sold aqua shade,it is blue die that filters the sun to kill the moss and algae it was about $40 a gallon but many customers liked it.its not a poison.this late in the year i would rake off what you can let the weather kill and start next spring or try ducks if possible i have 6 on a 1/4 acre pond and its clean as a pin.
whisker