Surface foam occurs when the water contains a high amount of dissolved organic material. It tends to be worse around areas of strong water movement, as these create bubbles of air in the water that strip out this organic material, bringing it to the surface as foam.
If you have an ultraviolet clarifier (UVC) fitted to your pond, you can treat it with Tetra Pond UVBooster to reduce the cause of the foaming. When exposed to ultraviolet light, UVBooster reacts to form substances that break down dissolved organic matter. This not only helps to reduce and control foaming, but also improves the overall pond environment.
If you don't have an UVC fitted, or if the problem is severe and persistant, the only option is to manually reduce the content of organic matter in the pond. If there is a lot of sediment at the base of the pond, this should be removed with a pond vacuum or by draining the pond down. At the same time, a portion of the water should be changed in the pond. Start by replacing 25% of the water with fresh tap water, taking care to treat the pond with Tetra Pond AquaSafe to remove chlorine and heavy metals. Repeat this if the problem does not go away – it is better to do several partial water changes, than one very large one. You should also ensure that the filter system is not too dirty, and if necessary clean it according to the instructions. Never wash biological filter media in tap water – always use pond water.
After cleaning the pond and replacing a portion of the water, add Tetra Pond CrystalWater to clear any suspended debris. To control the build-up of organic material in the future, add Tetra Pond SedimentMinus once every 2 weeks.