Our pond now has fish and has up until this exact moment been crystal clear and dog free. A few days ago yours truly noticed and unwanted plant appearing, blanket weed, closely followed by the fish developing a white fur. Fungus! So in order to preserve life of fish and get rid of unwanted weeds several concoctions have had to be added to the water. This has changed it from a clear liquid to this murky uninviting colour. Hope the fish like it.