What is this? Invasive moldy scum branches.

[Snow Drift]

I just opened my pool and I feel as if I’m in Stranger Thing’s upside down world. What is this and do I need to do anything beyond vacuuming it up? Please bear with the normal green stuff to clean.

It starts in my deep end, has a tall spire, and then branches up to my shallow end along the floor, before another branch is at the water line.

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[JamesW]

Maybe frog eggs?

 

[wireform]

That was the snake you lost track of when you were closing.