This is bugging me now, I can't seem to find where I read that the aquarium pest variety have a whip-like tail that they use to propel themselves through the water during the dark hours.
In my searching I did come across
this article by Ron Shimek
From it:
"The Sarcomastigophora is a large group comprised of organisms that move either by flagella or pseudopodia, or both. One of the interesting properties of flagella is that the long process or “hair” that is the visible essence of this structure (there are other internal, typically invisible, subcellular structures connected to the hair) may be withdrawn into the body of the organism. Thus, the organism may have a flagellum at one moment and lack one at some other time."
From what I gather, there are a lot of organisms that produce the "bubbly brown snot" or "cyano with bubbles" type of crud. Eradication procedure would be the same for all of them IMO