Every pond or aquarium must have a Dissolved Organic Compound (DOC) which is formed from the remains of feed and fine dirt that cannot be filtered. Increasing the DOC level will make the pool foam. To reduce DOC levels in ponds, a protein skimmer is a tool that is widely used in saltwater aquariums. However, nowadays it is starting to be widely used in Koi ponds. The function of the protein skimmer is to filter dissolved protein in the air by flotation through the air bubbles. Protein skimmers are inspired by natural phenomena on the beach during windy conditions. At times like this, usually, the edge of the beach will look foamy as a result of removing sewage in seawater. For more on this protein skimmer, you can read the O-Fish.com article.
Replacing old air with new air can also reduce DOC levels in the pool. But you need to know, air changes are not carried out as a whole. Ideally, the volume of air that is replaced is only 10-20 percent. Too much air replacement will only make the Koi fish stressful and new problems for your Koi fish. Koi fish is a very sensitive type of fish, especially to changes in pond conditions. Fish that are accustomed to long pond water conditions will be stressed if conditions change suddenly, especially changes in dissolved oxygen levels in the air. Another thing that needs to be done is to clean the filters in the pond, especially for those of you who are bio-ball and Zeolite stone filter users. You need to know, the zeolite used should be zeolite that has been specially processed for filters. Most of us don’t see that raw or never-before-found Zeolite is also a source of foam in koi ponds. You can get this zeolite that has come at a decorative fish shop at a price that is more expensive than the usual zeolite, of course.