Koi – The only magazine for practical Koi keeping advice


Although it doesn’t directly harm your Koi, foam is an unsightly pond problem. Ben Helm offers up some simple solutions to
this mess.

Water quality is the keystone to successful Koi keeping. Remove it and Koi health problems are likely to follow. Many different water quality parameters require constant monitoring with the results and interpretation of water tests essential to the maintenance of a healthy pond. Commonly tested parameters are those that are likely to cause the most significant problems: ammonia, nitrite and pH. Avoid assuming that only a handful of tests can give exhaustive analysis of the aquatic environment, but remember there are a vast array of other water parameters interacting within the pond which will go unnoticed and unmeasured, because Koi keepers assume that they aren’t harmful.

A protein skimmer is a simple and effective way to remove unsightly foam from your pond

Where does foam come from?
Something that occurs as a result of these interactions, but doesn’t significantly harm your Koi’s health, is foaming. This occurs where water is disturbed or agitated by a venturi or waterfall and the resultant bubbles will drift around the surface until they burst. These bubbles retain their shape because of the stabilising properties of complex dissolved compounds within the water. Largely organic compounds build up in the water to levels which encourage stable bubbles to form. Dissolved organic compounds are a by-product of the metabolism of Koi and other aquatic organisms, and are deposited into solution. 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 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 discoloured or foamy water.

Algae growth
It is common for water to foam as a result of excessive algae growth. Even if this is controlled by a UV unit, the proliferation of single celled algae can cause foaming using the organic compounds that are abundantly released into the water. If you use medications or pond additives containing vitamin complexes the water may foam, detracting from the spectacle of a calmed pond.

Solving the problem
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
By installing surface skimmers you can further prevent the build up of foam. This is a swimming pool technique whereby surface water is taken directly to the filter. Albeit an effective method it will only work with a submerged filter which, in time will recycle the protein and resurface the foam.

Protein skimmers
If bubbles want to form, then why not encourage them to do so under controlled conditions in a pond protein skimmer? Borrowed from marine fishkeeping, several pond models are available and through the vigorous aeration or movement of the pond water encourage the formation of a protein-rich foam which is collected and then removed. This innovation for ponds is probably the most intriguing method of reliably keeping foam to a minimum.

Heterotrophic: A living organism (including some bacteria) that gains its nutrients by feeding on other organisms (dead or alive). This compares with bacteria such as Nitrosomonas or Nitrobacter which uses chemicals as their source of nutrition.