Pond Fish

A pond is a beautiful and fascinating addition to any garden and ponds can be kept in most parts of the world, as long as you choose your species wisely. In many regions, fish will be able to spend the cold season in the pond. In climates where your pond might freeze across the entire surface it is better to house the fish indoors during the coldest months. Even cold tolerant species can suffocated in a small pond when gas exchange between the water and the air is prevented by a layer of ice. Species adapted to a very harsh climate can however survive by hibernating and staying in a dormant state where their metabolism is extremely low and they consume very little oxygen.
The two most commonly kept fish types in garden ponds are Goldfish and Koi. Goldfish can be kept with most aquatic plant species, while Koi fishes like to eat plants and can be kept only with a few plant species. Since Koi grows larger than Goldfish, Goldfish is a better choice if your pond is small. Koi fish should not be kept in ponds smaller than 1000 gallons, and the pond should be at least three feet deep, preferably even deeper. Goldfish can be housed in a pond that is no deeper than two feet, but if you live in a colder climate and you plan to let your Goldfish stay in the pond during the winter the pond must be deeper. Goldfish need at least 12-16 inches of water below the freeze zone to survive.
If you create a garden pond from scratch, you should ideally make it quite large since a large pond is easier to maintain than a smaller pond. A large pond will provide your fish with a more stable climate. Pollutants that enter the pond from outside will be diluted by larger water mass, and the same is true for plant and fish waste. A large pond is more resilient to rapid temperature changes and there will typically be easier for the fish to hide if a predator, such as a cat or raccoon, venture into the pond. With a large pond, you will also be more flexible when choosing fish and plant species. It is also safer for fish to stay in a large pond during the winter.
Location is important when creating your new pond. If you place your pond under trees or bushes, you must regularly remove leaves and other debris from the water since it will carry to much organic compounds to the small water mass. Fish-only ponds can be placed in shaded areas of a garden, but if you want to keep plants they might have other requirements. Water lilies will for instance do best in a pond that receives at least 4-6 hours of direct sunlight each day. Fish-only ponds will require more maintenance work than planted ponds, since waste products from fish are consumed by plants. Unplanted ponds will therefore require more filtration and they are more prone to algae growth. If this is your first pond, you should ideally choose a sturdy plant species that is capable of consuming a lot of fish waste and produce a lot of oxygen. If your pond receives a lot of sunlight, it should also be planted with some surface leafed plants that will provide the fish with shade during hot days.