p>Although it doesn't directly harm your pond fish, foam is an unsightly pond problem. Pond foam occurs as a result of interactions with a vast number of usually untested water parameters. Foaming occurs where water is disturbed or agitated by a venture fountain or waterfall and the resultant bubbles will drift around the surface until they burst. These bubbles retain their shape because of the stabilizing properties of complex dissolved compounds within the water. Protein levels within the water can also rise through the inappropriate use of higher protein diets, which can leach other soluble compounds into the water, also leading to the formation of foam on the water's surface. Such organic compounds are not broken down by the bacteria that work on ammonia
, nitrites and nitrates
but by a host of heterotrophic bacteria, a living organism that gains its nutrients by feeding on other organisms (dead or alive), which go to work on this diverse range of pollutants. These bacteria feed on oxygen and are unable to completely breakdown these organic compounds which may cause discolored or foamy water.
Because the accumulation of soluble organic compounds forms bubbles, regular and frequent partial water changes should prove successful in eradicating foam. Diluting old pond water with fresh water should reduce the formation of bubbles. Organic compounds often enter the water through food, so try different diets and eventually you'll find one that will reduce the creation of foam. Excessively high protein levels or diets that leach significantly quicker than others will also lead to a build up of bubbles as these can fuel the onset of algal growth. Such measures will also reduce the amount of algae in your pond and their secretions into the water.
Surface skimmers can further reduce the build up of pond foam. This is a swimming pool technique whereby surface water is taken directly to the filter. Another control technique is by the use of a protein skimmer. This technique is taken from marine fish keeping. The basic premise it to encourage the bubbling under controlled conditions in a protein skimmer. This produces protein-rich foam which is collected and then removed. This method is probably the most intriguing method of reliably keeping foam to a minimum.
To find products to help treat ammonia buildup, check out Pond Maintenance > Water Treatments > Water Quality