My pond started showing this same symptom 2 days ago, the pictures posted look identical to what I'm seeing. I do have a microscope so I took a look to see if I could identify what was causing the brown film. It was really easy to make the prep by laying the glass slide on top of the film and the scum adhered. There is no odor to the water.

What I saw was predominately a lot of simple, single cell structures, some were clumped together and the cell walls were green even though the film looks light brown on my pond. I'm not an expert but I think this is planktonic algae. Maybe someone with knowledge in this area can verify for me. I saw a few other plankton on the slide that I could positively identify, Scenedesmus and Cyclotella. I did not see anything that was filamentous or branching and I have not had any FA since my pond was re-dug 2 years ago, knock on wood.

The slide also had very active moving organisms even though the slide appeared dry to my naked eye. There were some Paramecium and what I believe is Chilodonella in greater numbers. That's about it, not too exciting.

I have a 15' floating hoop made out of 1" pvc tubing that corrals my water hyacinths and there is no film inside the hoop so the hoop is keeping the film back. If this were pollen I would expect to see it inside the hoop.

I found this link that might help someone Algae Identification Field Guide

Background on pond:
My pond is 1/4 surface acre with Spotfin shiners and Bluntnose minnows, 13' deep at full pool but right now the water is down 2'. I haven't made a secchi disk yet but visibility is less than 2'. Water temperature is 85! I checked the water temperature a few days before the film appeared and it was 82.

I have a Vertex XL-5 that I've been running 24/7 and I add beneficial bacteria. I'm also trying a product that I can get local called EcoBoost which is supposed to help clear the water. The MSDS on EcoBoost says it's composed of Lithothamnium calcareum, an algae! The product is supposed to bind phosphates and my research shows that it softens water.



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