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

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

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

Without the correct level of oxygen , the fish exhibits symptoms of stunted growth, poor respiration, which leads to a weakened immune system and, as a result, disease. Also, koi look lethargic, don't swim well, and are stressed.

What is pond aeration ? 

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

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

What is important in winter? 

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

Intensive feeding is therefore not necessary, on the contrary, it is harmful. In the winter, the fish consume the nutrients from the fall and live off whatever they can find in the water, on the plants, or on the bottom soil. Once a week they can also be fed a few treats. However, fish respiration remains a vital issue and pond aeration should therefore be taken seriously.

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

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

In winter, the water temperature in a frozen pond varies from 0° in the upper layers close to the ice to +4 to +6° C in the lower layers. The 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. Therefore, the water at the bottom is saturated with these toxic gases, which can cause suffocation of fish.

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

In order for the fish to get enough oxygen and not suffocate due to oversaturation of the water with nitrogen compounds and carbon dioxide, you need to aerate the pond, that is, remove nitrogen compounds and carbon dioxide. CO2 from the water and oxygenate it. This is called pond aeration and it can be done in different ways.

What are the other oxygen consumers in water?

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

Bacteria that process harmful fish waste also use oxygen from the water. So in a dirty pond or 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. These are carbon dioxide and methane 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 be weather dependent and decrease each night. Indeed, aquatic plants and algae produce oxygen by photosynthesis, using sunlight. In cloudy weather and at night there is less light and therefore the level of oxygen decreases.

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

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

It is very important to know when supplemental 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 cling to the air at the surface.
• The fish congregate around the fountain and in the most oxygen-rich places.
• Lots of trash in the water
• Persistent odor, many gas bubbles on the surface of the water

How do I oxygenate my pond?

There are several ways to increase the oxygen in the pond. Oxygen dissolving on the surface of the water, the most effective is to increase this surface. This can be done with waterfalls, 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 pond:

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 Elodia crispa, which produce oxygen.

FAQs

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

Which air pump to choose for a pond from 1000 to 10,000L?

Here is the kit that we recommend for a pond of 1000 liters to 10000 liters with koi carp. It is useless to put more raise in oxygen rate with a density of "normal" fish.