How to choose an oxygenator or air pump for koi carp?

How to choose an oxygenator for koi carp? How to choose an air pump for my koi carp? Like most other living creatures, fish need oxygen.

Fish are able to obtain oxygen from the water through their gills, which are analogous to lungs. Koi use oxygen in almost all of their life processes, including digestion and growth.

Without the right level of oxygen, fish show symptoms of stunted growth and poor respiration, leading to a weakened immune system and, consequently, disease. Furthermore, koi appear lethargic, do not swim well, and are stressed.

What is pond aeration?

It is the process of adding oxygen to water. Oxygen molecules from the air dissolve at the water's surface, which is where most of the oxygen enters the water. Water is capable of storing oxygen in a dissolved state. Characteristically, cold water can store more oxygen, which explains why all problems involving a lack of oxygen occur in summer when the temperature is quite high.

Other factors also influence the level of oxygen in the water, such as the number of fish, the size of the filter, water circulation, and the size of the water surface. The larger the surface area, the more oxygen is dissolved in the water (through a natural phenomenon called mass transfer by concentration gradient).

What is important in winter?

Pond aeration in winter is one of the most important conditions for the successful overwintering of fish. Fish also need to feed and breathe in winter. The water temperature is low and the fish's metabolic processes and growth are slowed down during this season.

Intensive feeding is therefore unnecessary; on the contrary, it is harmful. In winter, fish consume the nutrients from autumn and live on whatever they can find in the water, on plants, or on the bottom. Once a week, they can also be fed a few treats. However, fish respiration remains a vital issue and therefore pond aeration must be taken seriously.

Several important and interdependent factors determine the living conditions of fish in the pond:

• water temperature,
• lighting,
• oxygen content of the water,
• nitrogen content of the water.

In winter, the water temperature in a frozen pond varies from 0° in the upper layers near the ice to +4 to +6°C in the lower layers. Fish prefer to stay in the warmest part of the pond and the lower layers.

Nitrogen compounds, which are harmful to fish, are also concentrated in the lower layers. Consequently, the water at the bottom is saturated with these toxic gases, which can cause the fish to suffocate.

The oxygen needed for respiration is supplied either by plants that consume carbon dioxide and produce oxygen through photosynthesis, or by the direct contact of water with the air.

To ensure that fish have enough oxygen and do not suffocate due to the oversaturation of the water with nitrogen compounds and carbon dioxide, you must aerate the pond, i.e., remove nitrogen compounds and CO2 from the water and oxygenate it. This is called pond aeration and it can be achieved in different ways.

What are the other oxygen consumers in the water?

Poor water circulation in the pond can create "dead zones" where oxygen dissolves the least. This usually happens in the deepest parts of the pond.

Bacteria that process harmful fish waste also use oxygen from the water. Thus, in a dirty pond or one with an excessive number of fish, there will be more problems with low oxygen levels.

You may have noticed bubbles rising to the surface from the depths of the pond. This is carbon dioxide and methane resulting from the recycling of waste by bacteria. If the pond filter is not the right size, the amount of waste increases, and with it, the problem of bubbles.

Surprisingly, dissolved oxygen levels can depend on the weather and decrease every night. This is because aquatic plants and algae produce oxygen through photosynthesis, using sunlight. On cloudy days and at night, there is less light and therefore the oxygen level decreases.

The use of chemicals when treating diseases also rapidly removes oxygen from the water. Thus, any means of treating algae, for example, green water, quickly leads to a drop in the oxygen level. It is therefore necessary to increase the oxygen level in the pond for several days during koi treatments.

In autumn, when extra debris in the form of fallen leaves appears in the pond, the oxygen level also decreases, which is not very noticeable when the water is cold, but in spring, the consequences can be dramatic, as the oxygen level drops within hours when the water warms up. It is best to clean the surface of the pond before winter arrives.

It is very important to know when extra oxygen is needed. You can do this by observing the behavior of the koi, which will change if there is a lack of oxygen.

Common signs of a lack of oxygen in a garden pond:

• Koi gasping for air at the surface.
• Fish gathering around the fountain and in the areas richest in oxygen.
• Lots of waste in the water.
• Lingering odor, many gas bubbles at the water's surface.

How to oxygenate my pond?

There are several ways to increase oxygen in the pond. Since oxygen dissolves at the water's surface, the most effective way is to increase this surface area. This can be done with waterfalls or fountains that agitate the water, producing oxygen. A second pump can be placed closer to the surface for the summer, which will also increase circulation.

Four ways to aerate a pond or garden pool:

1. Use an air pump.
2. Use fountains, waterfalls, and surface-mounted pumps.
3. Add aquatic plants to the pond.
4. You can use aquatic plants, such as Elodea crispa, which produce oxygen.

FAQ

Which air pump to choose for a pond of less than 1000L?

Which air pump to choose for a pond of 1,000 to 10,000L?

Here is the kit we recommend for a 1,000 to 10,000-liter pond with koi carp. There is no point in having a higher oxygen rate with a "normal" fish density.