How Feeding Can Affect Water Quality

Every environment shares problems if the inputs into the system are out of balance with the rate at which they are removed or broken down. Currently, on the global basis, this is the case with CO2 and the earth’s atmosphere and it is also true for every koi pond, where the regular addition of food into the pond environment will unavoidable lead to a change in the water quality.

It is helpful to understand the various implications for both koi and koi pond that are being fed regularly, the reasons why particular changes in water quality occur and the measures we can take to reduce them.

The stability of our pond environment is going to be threatened through the activities of feeding at many different states from the moment the food hits the pond’s surface through to its digestions, assimilation and excretion and ultimate collection in the pond filter.

The impact of feeding on water quality. Leaching. Water is the world’s best solvent and will readily draw solutes out of food, the moment the two come in to contact. Many water-soluble compounds in foods (most vitamins and minerals) will have a tendency to leach out of the food into the water and the longer the food is in the water before being consumed, the more extreme the leaching is likely to be. There is a danger of leaching making food nutritionally deficient, but most food manufacturers recognize this potential problem and ensure that food contains excess levels of water soluble vitamins. However, even a tiny degree of leaching is inevitable at each feed, causing nutrients to accumulate in the pond water, thus altering the water chemistry. Therefore, even through the natural course of feeding, the balance of the pond’s chemistry is under threat.

Pre-soaking Food ? With the extent and speed at which leaching occurs, it should really bring in to question the practice adopted by a number of KOI Keepers, of pre-soaking food in the belief that it aids feeding and digestion. Pre-soaking food will cause most of the water soluble nutrients to dissolve, increasing the speed at which they leach into the pond. Is this good for water quality and koi nutrition?

Ingestion, digestion and assimilation. Even if koi consumed their food the second it was offered, feeding would still be implications for water quality, through their breakdown and utilization of food.

As koi are cold-blooded and the metabolism ( biological tick over rake) is governed by water temperature, it is logical that they are offered different types of diet at different temperatures.

There is no reason why koi cannot be offered a summer diet all year round, as koi will simply digest and assimilate ( take up and utilize) what they require, excreting any surplus. However, feeding a summer growth food all year round will have a detrimental effect on water quality ( which in turn will affect koi health) by the levels of food excreted by koi.

What makes a summer food different from an autumn food? As summer is the warmest period of the year (allegedly) it is the period when koi will utilize their food for both growth and storage of energy for the follow winter period that is anticipated by their physiology. Consequently, such diets are high protein and high energy diets, ready to satisfy their increased nutrition demands. Yet if these diets are offered when koi cannot utilize them efficiently, then levels of excretion will be increased having a knock-on effect on water quality. Excess protein in particular is likely to affect water quality.

If protein in the diet is in excess of what koi require, koi will not utilize all of the protein in the diet for growth, but either break it down and burn it for energy or excreted high levels undigested.

Protein is made up of 4 elements, carbon, hydrogen, oxygen and nitrogen. When protein is used as a source of energy, koi utilize the carbon, hydrogen and oxygen element, but excrete the nitrogen in the form of ammonia. Consequently, too much protein in the diet is likely to lead to an increase in the levels of ammonia excreted by koi.

In addition, the undigested proteins excreted by koi ) along with other organic material, will attract significant bacterial action by oxygen demanding heterotrophic bacteria. Interested in the organic element of the waste, such bacteria will also lead to an additional release of ammonia into the water. When koi are ever subjected to excess food ( both quality and quantity) it will have serious implications for water quality, but if your filtration is adequate. Will, avert any short term toxicity problems (ammonia) but still ultimately lead to build up of nitrates. The accumulation of excreted products (both solid and soluble) will also lead to further noticeable changes in water quality.

Build up of soluble organics. The accumulation of soluble organic pollutants either directly from food or indirectly from excretion will cause water to become discolored, often taking on a yellowish tinge. This may also be accompanied by excessive frothing that is caused by the build up of soluble organic matter, created around waterfalls and venturis where pond water mixes vigorously with air. The presence of a high organic content in the water causes the formation of stable bubbles, that do not readily burst.

Build of of Inorganics. Besides the accumulation of nitrates after the filter’s handling of ammonia, feeding can also cause quite a build up of other inorganic compounds-particularly phosphates and sulfates.

Although not as directly observable as organic compounds that cause discoloration and foaming, phosphates can lead to the proliferation of algae. As most koi ponds are plant free and fitted with a UV lamp to kill green water, blanketweed is likely to proliferate in such a nutrient-rich and competition-free environment.

Reducing the Impact. In the current fight against global warming, we recognize that a proportion of CO2 emissions can be added through careful management and the use of alternative energy sources. The same is true for reducing the impact of feeding on a koi pond where the main objective is maintaining healthy koi and to provide them with a stable and healthy pond environment. Having identified that feeding can cause both short-term and long term instability to water quality, our koi’s health will benefit if we can reduce such instability.

Measures to reduce the impact of feeding on koi pond instability.

1. Feed the most appropriate diet: Ensure that koi are offered the protein and energy content they require and can most adequately utilize. This means feeding lower protein diets at cooler temperatures, moving to a higher protein diet when the water warms up..

2. Feed on basis of a little and often: If too much food is offered at any one time, nutrients have longer to leach out into the water. Not only does this risk causing fish deficiencies, but will also taint the water color and lead to the proliferation of algae.

3. Reconsider pre-soaking food before feeding.: Pre soaking food pre-leaches nutrients prior to adding the food to the pond.

4. Water changes: The best strategy for creating a stable water quality is not to leave lengthy periods between water changes. This keeps you on top of any build up of food-related compounds and ensures that the addition of freshwater is not too dissimilar ( and therefore stressful) to the pond and to koi.

5. Protein skimmer: The installation of a protein skimmer can be a useful tool in removing dissolved organic compounds from the pond water. It should not be used in place of regular partial water changes, but may allow you to reduce the frequency of water changes.

In Summary: We feed our koi to enhance their health, growth and coloration, but in doing so, unintentionally present our pond with potential water quality problems which must be managed to maintain a stable and healthy pond environment.