Are you adding the chlorine remover according to the directions? You don't want to overdose the stuff.
The kind of foam you are describing sounds like a buildup of organic matter. Do you have a lot of aeration or turbulence in the water especially during the night? Usually proteinaceous matter like dissolved organics (feces, uneaten food, bacteria, decaying leaves, etc.) will adhere to the water/air interface often seen as a film or scum layer on the surface of stagnant water. When you churn up the water and introduce a lot of bubbles into the water, over a period of time you will see this protein foam accumulate on the surface.
Much like the brown foam you can see along the beaches especially when the water is choppy. It's one of nature's ways of removing excess nutrients from the ocean. The wind then blows the foam on shore across the grass where it can become fertilizer for the plants.
In the saltwater reef hobby we use expensive protein skimmers which mimic this action in the ocean by injecting millions of very fine bubbles into a vertical column of water at very high speed. As the aquarium water passes through the tube the organics are removed and bubble up to the top where they spill over and collect in a container of brown smelly scum. Actually, some sewage treatment plants utilize this kind of technology too.
One other thought...there's a lot of pollen in the air this time of year. That could also be contributing to the buildup of organic material in your pond. You may want to think about increasing the capability of your filter. You should also scoop out the foam as it accumulates on the surface.
