I think it’s D vacuoles, I’m not certain but it don’t hurt to try if it’s not that try A
To grow food to grow food
At the end of the winter they are most numerous in fresh water. they will cover surface of aquatic plants or poles and wooden borders of ponds. If you like to study them you can scrape the brown growth with a flat piece of plastic. you can also use a sponge. for the free living (plankton) species fine mesh plankton net is very useful.
