These green structures were growing on mud. What are the chances that this is a species of Spirogyra?

Looking at this, it seemed like sexual reproduction was going to occur…

And its cell wall shows birefringence!

Lurking in these algal jungle was a creature strange. It was a rare sight that I could get to see only twice. the second time I recorded it. Is it a rotifer?

Once I had grown a twig of a weed in a glass beaker. It survived for several days. One day I had dropped a bunch of these thread-like structures in the beaker. The next day that weed died and shrivelled totally. I wonder if there is a relation between the two…