I too have experienced water marks with ussing too much Photo-Flo. Only a drop or two are needed for each 250 ml. You need just enough to break the surface tension of the water. The problem seems to be with the anti-foaming agent that Kodak uses, a tallowate. As the name implies it is made from grease. The other active ingredient is Triton X-100.
A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.