I'm going to tell you what I did when this mystery sludge showed up in my pond this year. I saw all the bubbles and stuck my hand on the liner, rubbing my hand along it. The algae instantly let go and started to float. I was unsure if this was bad or good gook, so I watched it for a few days and noticed the up and down motion it has during the day/night. After a while I was feeling froggy, so I got into my pond and rubbed as much of it as possible so it'd float up. I grabbed it out, mostly with my hands *ugh - just like snot* because it'd go thru nets. As I got it off the liner and off the top of the water it disappeared, that is unless I missed a bit. I figured, ah, it's a pond - who cares about a little goo? and left it alone. As time went on it became a strand until it reached the top of the water. I think it's some sort of string algae in it's early stages. First the bubbly stuff on the liner, then the goo on top of the water, then the string algae. So- I just suggest removing as much manually as possible, but try to get all of what you knock loose. I think it's like some weed grasses where each piece you break off becomes a new plant. Also, when you get the most you can out, do kitty litter. It really helps. Skim, skim, skim and clay, clay, clay! Hope that doesn't confuse you more.
