I'm with Dan....I add about 4-5 drops per liter (much less than 1:1000) and a splash (a tablespoon maybe) of isopropyl alcohol. I went with a lower amount of photoflo because it tended to leave marks on my film in my water (Lake Michigan). Photoflo and alcohol act in different ways to change the surface tension. There are other surfactants like SDS or igepal but I figure that Kodak had smart chemists so I'll go with photoflo.