Valonia Bubble Algae

This is one of the largest single cell organisms. They typically grow as an individual as shown here but I have also seen them grow in small clusters.

The valonia is attached to the surface via rhizoids which can be thought of something like a root. It is pretty strong and can make removal of this algae difficult.

I find it is easier to remove this bubble algae if you can twist it much like how you would unscrew a light bulb.This can break the rhizoids without popping the bubble as the bubble may contain spores which will generate new valonia bubbles.