Hey all. Newbie here. I was hoping somebody could help me with a foam issue. I have a 4' x 5' x 3' deep pond and until recently I've just had a 400gph pump sitting on the bottom with piece of PVC pipe sticking straight up out of the pond to act as a fountain with no filtration. So yesterday I drained about 90% of the water out of my pond to do some maintenance and also to install my new tetra pond waterfall filter. Filled my pond back up, started my filter And in no time had foam covering the entire surface of my pond. I stuck my water hose in it and overflowed the pond to get rid of the surface foam, started it back up and in a couple of hours had foam again. Overflowed it again and still foam. Now researching pond foam on the Internet tells me that the cause is DOCs but how can this be when I'm up to almost a 100% water change as well as a new clean filter?