This is a natural pond with no liner, We recently bought our house and it was here with it but I do eventually want to be able to put koi in there and maybe make a sitting area. while I know all the lily pads in the middle are good for it I'm completely lost when it comes to the white fluff around the edges. The bottom in the center is clear but there's what looks like long stringy grass growing all around the shallow ends with a layer of green but mostly white spongy growth floating on the surface. I included pictures below this because it's hard to describe and I probably didn't do that well explaining it lol. Thank you in advance to any one that can help with this.