Q: There is a brown rust-like film/oil slick covering my pond. Do you have an idea what this might be and how to get rid of it? - Several Customers
A: There are several things this could be: Algae, duckweed, watermeal or pollen.
Determining if Algae is a Problem: Filamentous Algae will float around the pond’s edges in mats while Planktonic Algae will make the whole body of water to look like a “pea soup” green color. If this is the case, using Algae Defense Algaecide will provide quick control. Follow up with Pond-Clear for long-term clear water.
Determining if Duckweed or Watermeal is the Problem: Duckweed and Watermeal are very rapid growers and will cover an entire pond if they get out of control. Looking to the pictures to the left, you can see that Duckweed is a small plant the size of a pencil eraser, while Watermeal is about the size of the tip of a pencil. If you determine that you have Duckweed or Watermeal, your only long-term option is WhiteCap Aquatic Herbicide. If you only require short-term control (3-4 weeks) for an event or party PondWeed Defense may be used.
Determining if Pollen is the Problem: What may look like a greenish, brownish algae, may actually be pollen. Pollen may even cause an oil-slick or film on the surface of the pond. There is no magic product that will give you a quick fix. Many times a heavy rain will settle it to the bottom. In many cases if your pond receives good circulation from an aerator or fountain you will not see pollen becoming much of a problem.
Filed under: Algae Control, Duckweed, Pollen, Pond & Lake, Watermeal Tagged: | algae, Duckweed, filamentous algae, film, green water, identifying algae, identifying duckweed, identifying pollen, identifying watermeal, oil slick, pea green allgae, planktonic algae, pollen, Watermeal