Water quality is the keystone to successful koi keeping. Remove it and koi health problems are likely to follow. There are many different water quality parameters that require constant monitoring with the results and interpretation of water tests essential to maintain a healthy pond.
he most regularly tested parameters are those that are likely to cause the most significant problems, such as ammonia, nitrite and pH and there is often the risk of assuming that only a handful of tests can give exhaustive analysis of the aquatic environment. There are however, a vast array of other water parameters interactions within the pond which will go unnoticed and unmeasured, purely on the basis and assumption that they do not have significant affects on koi health.
One such phenomenon that does occur as a result of interactions within a pond but does not have a significant effect on koi health is foaming or the formation of very stable bubbles on the surface of the pond. Where water is disturbed or agitated at a venturi or waterfall, then the bubbles that form, rather than bursting will remain, and drift around the pond surface for minutes until they do eventually burst.
These bubbles are formed through the stabilising properties of complex dissolved compounds. These largely organic compounds, build up in the water over time to levels which encourage stable bubbles to form.
Dissolved organic compounds build up through the metabolism of koi and other aquatic organisms, depositing the products of digestion into solution. Protein levels within the water can also increase rapidly through the inappropriate use of higher protein diets, which can leach other soluble compounds into the water, leading to the formation of a foam.
Such organic compounds are not broken down by the bacteria that work on ammonia, nitrites and nitrates but by a host of heterotrophic bacteria go to work on this diverse range of pollutants. These bacteria are oxygen consumers and are often unable to completely breakdown these organic compounds. In extreme cases, these can lead to the discolouration of the pond water.
Other likely causes of foaming.
It is common for water to foam as a result of excessive algae growth. Even if this is controlled by a UV, the proliferation of single celled algae can cause water to foam through the organic compounds that are abundantly released into the water.
The use of certain medications or pond additives, particularly those containing Vitamin complexes (water conditioners) can also cause the water to foam, detracting from the spectacle of a calmed pond.
Solving the problem
As it is the accumulation of soluble organic compounds that assist in the formation of bubbles, regular and frequent partial water changes should prove successful. The simple act of diluting old pond water with purer, less organic-laden tapwater should reduce the formation of bubbles.
Bearing in mind that the most likely route through which organic compounds enter the water is through food, it may be prudent to try different diets to find one that will reduce the tendency for your pond to foam. Excessively high protein levels, or diets that leach significantly quicker than other diets will also lead to the annoyance of bubbles. As these can fuel the onset of algal growth, such measures will also reduce the occurrence of excessive algal growth and their secretion of proteins into the water.
In addition to the preventative measures above, quite an extreme measure of controlling the formation of foam is the installation of a surface skimmer. Borrowed from the swimming pool industry, surface skimmers are used as a means of taking water from the surface straight to the filter. Consequently, although these are effective, they are only practicable with a wet/submerged filter installation, and only recycle the protein for it to reappear and cause a foam again.
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 water movement encourage the formation of a protein-rich foam which is collected and then removed from the pond water. This innovation for ponds is probably the most intriguing and reliable method of reliably keeping foam to a minimum.