"is it something that can be bought or grown?"
My 2 cents is, If I am correct, that ia a Fresh water algae from back when we worked with ponds. Looks Just like Green Hair algea in a dirty salt tank. "we had to learn some of this stuff when we did the pool and pond stuff"
can it be Bought? I would say ya, but most who that would have it would say take all of it. "hehehe."
Can it be grown? Just find someone with a Dirty pond, I bet they would say yes.