Which fish to choose for an outdoor pond?

Creating an ideal environment for healthy fish

For the well being of the fishes, the pond should be placed in a sunny place. Plants planted around the pond will protect your fish from the sun in warm hours, as well as surface aquatic plants such as water lilies. Plants also have the advantage of eliminating nitrates and phosphates, and therefore help to clean up your pond. However, many pond fish, especially koi carp, tend to eat plant roots: you can place stones or a net around your plants to protect them. Ideally, it is best to avoid placing your pond in the immediate vicinity of a tree, as falling leaves are a major source of water pollution. Dead plants and leaves should be removed as frequently as necessary.

Small ponds are subject to large fluctuations in water quality and temperature. Consideration should be given to controlling the parameters using commercially available kits. Larger ponds provide more stable conditions for fish, as their large volume dilutes pollutants. For the most common pond fish, the water should have the following characteristics * :

-pH between 7 and 8.5,

-Nitrite and ammonia levels less than 0.1 mg/l,

-Nitrate level less than 50 mg/l,

-Calcium carbonate between 100 and 300 mg/l.

Make sure to clean the filter regularly as it can become clogged quite quickly. Also provide a strong net in case you need to catch your fish to care for them, or to move them around.

Your fish will not find the food they need in the pond to survive all year round. So you should feed them with a commercially available pond fish food. For most fish, 30% protein is necessary because it is an important source of energy. This food can be in the form of flakes, sticks, or pellets that float or sink. The choice depends on the type of fish you have; sturgeons and tenches will prefer food that sinks because groundfish, carp and Ides eat more on the surface and prefer food that floats. If you only have one type of fish in your pond, there are specially formulated foods for each species. Koi carp and goldfish are omnivorous but mainly eat plants.

It is not necessary to feed your fish every day, they can fast for a while. If your pond is well planted, food intake from outside the pond can be reduced. During the warm months you need to feed your fish more, on the one hand because their needs increase with the temperature, and on the other hand to prepare them for winter. On the other hand, below 8°C their metabolism is extremely slowed down and it is useless to feed them. In any case, be careful not to give too much food: if everything is not eaten in 2 or 3 minutes, the uneaten food must be removed from the pond and, in the future, reduce the quantities.

Finally, always remember to respect a quarantine before introducing a new fish in your pond. For large fish, you can, for example, use a children’s pool covered with a net to protect your fish from predators. Avoid direct sunlight, and place the quarantine container away from the water.

It is not advisable to introduce fish taken from the wild into your pond because of the high risk of introducing pathogens and parasites.

Finally, as with aquarium fish, leave the newly purchased fish in its bag for about 20 minutes to allow time for the temperature of the pond to equilibrate.

The different pond fish

Most fish live for about 15 years. Goldfish and koi carp can even reach the age of 25 years if conditions are optimal.

  • Goldfish (Carassius auratus)

The common goldfish is very common in the ponds. It is a very resistant fish, which also proliferates quite rapidly. Therefore, beware of overpopulation. Once adult, it can reach up to 30 or 40 cm in length, but 20 centimeters is a more frequent size.

The Comet Sarasa (red and white color) and the Shunbukin (red, orange, black and white) are two small varieties which will not exceed 20 centimeters.

The other varieties of goldfish (telescope, lion’s head, black moon) are more sensitive to extreme temperatures, but also to predators because they move more slowly. They are more fragile and therefore less adapted to pond life.

It is also possible to raise goldfish in an aquarium, and release them in your pond towards the May month.

  • The Ide (Leuciscus Idus)

The Ide is a silvery-white fish, known to slow down the proliferation of other fish by feeding on their eggs, and insects by eating their larvae. They also eat plant debris. The Ide helps to regulate the ecosystem of your pond. It is a gregarious fish that lives in schools, which requires the introduction of at least 5 individuals. Once adult, it can reach 70 centimeters. The Ide is a lively fish, it moves very quickly and on the surface of the water.

  • The tench (Tinca Tinca)

The basin tanchs are generally Mongolian tanchs. Once adult, these fish reach almost 50 centimeters, and live mainly at the bottom of the pond.

  • Koi carp (Cyprinus carpio)

Koi carp can reach a very imposing size, ranging from 60 to 90 centimeters long. These fish are quite easy to tame, and come without difficulty in contact with humans. This is especially observed during the distribution of food, because it is not rare that carps come to eat in the hand. They can cohabit with other species of fish as long as the size of your pond allows it. There is a wide variety of Koi carp in a multitude of colors: white, black, red, orange, pale blue….

  • Sturgeon (Acipenser ruthenus)

The sturgeon can be up to 1 meter long, or even longer. It is a groundfish. It requires a large size pond and low in algae and plants.

  • Love carp or herbivorous carp (Ctenopharyngodon idella).

Love carps should be reserved for ponds; these fish need a very large water surface, rarely available in the case of ornamental ponds. In addition, they are herbivorous and eat all the plants in your pond indiscriminately, which can quickly upset its balance.

Adapt the species to the size of the pond

There are two scenarios:

-either you have installed a pre-formed, plastic basin that you have purchased commercially. These basins are most often small in size. The minimum size for a fish introduction is 2.5 x 1x 0.5 meters. The depth of 50 centimeters is the minimum depth for fish to be protected in winter. With this pond size you can only introduce goldfish. Other species are not suitable. You can count about 0.1 m3 of water per goldfish.

-either you have had the pond built, and depending on its size you may have more choice regarding the species to introduce. A pond of 3 x 2.5 x 1 meter* is the minimum required for tench or koi carp. Ides need a minimum area of 20 square meters. It is necessary to count 1 m3 of water for a single koi carp, a tench or an Ide, knowing that the latter live in schools of at least 5 individuals. As for sturgeons, they are reserved for very large pools, as an individual needs about 15 m3 of water to fully develop.

You can also add other animals such as frogs to your pond.