black ball like things that grow....

[MichelleW]

Help!
I have something growing in the pool and I can't get rid of it!

It starts as little black balls on the surface of the pool cover (which was have cleaned with every cleaner possible and they still show up.) I am starting to think they are falling from the maple tree that's beside the pool since they only seem to be on that side of the cover in the shade. If those little black balls fall in the pool through the holes in the pool cover, they almost instantly blossom into a 6 sided flower shaped green fuzzy thing. And then they multiply and get bigger. I am assuming it's some kind of algae but the algecide and high levels of chlorine isn't stopping the growth of it.

Any suggestions/ideas on what it could be? They're easy enough to vacuum up - but it's annoying me!

--Michelle