What are your goals with the fish in your pond? Do you just want to have a few little fishies lazily swimming around in the water? Or, do you want large, championship quality koi? These two goals are very different and result in very different approaches to feeding.

In a typical backyard pond, the fish will derive some of their nutrition from algae, microscopic organisms and other particles in the water. Depending on the sophistication and size of your filtration system, this may be enough to support a small population of fish by itself.

If your goal is just to enjoy a few fish, you may get by with only feeding the fish occasionally with a supplemental source of nutrients. Remember that the more you feed the fish, the larger they get and the more waste they produce. This adds to the nutrient enrichment of the pond and increases the algae load. 

People interested in growing championship quality koi, on the other hand, will face other challenges. You will need to have a more elaborate filtration system because, generally, you will be keeping a higher fish population (both numbers and size). This will boost the nutrient concentrations in the water and the amount of organic gunk on the pond floor.

Most backyard pond owners tend to be somewhere between these two extremes. They are not into showing their fish at koi shows but they think of their fish as more than just accessories in the pond. They often treat the fish as if they were another family pet. Each one has a name and a personality as defined by their owner.

This type of relationship is great as long as it does not get overdone. Too often, we see family dogs waddling down the street, barely able to put one foot in front of the other because they are grossly overweight. Their owners just cannot resist the temptation to feed little Fido at every turn. Our kindness can actually lead to illness and premature death of our beloved pet.

When this behavior is carried over to our pets in the ponds, we end up doing them the same disservice. By overfeeding the fish in our ponds, they grow larger and produce more waste products. One problem, of course, is increased algal growth but there is a secondary, potentially more serious problem.

When the detritus drops to the bottom of the pond, it contributes to the build up of gunk. Gunk decomposes and releases gases such as ammonia into the water. When these gases begin to displace the oxygen in the water, eventually, it will affect the fish. In the winter, if the ice freezes over the top of the pond and traps these gases, the fish may be killed.