I think something should be clarified about using dishwashing detergent. The only thing that will work is the liquid that is sold for HAND WASHING of dishes in the SINK. Under no circumstances should you use the gel that is sold for using in a dishwasher. This is a very caustic substance.
Photoflo contains a surfactant, which lowers the surface tension of water, thus causing it to sheet off, rather than puddle into droplets. Dishwashing liquid contains a surfactant as well as detergents. So, they are not the same, but they do exhibit the same qualities in regards to lowering the surface tension of water. Whether the minute traces of detergent left on the film are detrimental, I don't know. But I DO KNOW that you could only possibly use the liquid "soaps" designed for HAND WASHING of dishes.