Why do my fish stay at the top of the aquarium?

Naturally, aquarium fish evolve at different depths in the aquarium. Although some strains prefer to stay on the bottom, others will appreciate the middle or upper regions. However, if you find that the fish spend the majority of their time at the surface of the water, this could indicate an underlying problem.

A breathing problem

When fish stay close to the surface, it means they are trying to breathe more easily. Indeed, fish breathe thanks to the presence of their gills. The latter make it possible to capture dissolved oxygen, without association with the H2O molecule. Dissolved oxygen levels are generally higher closer to the surface, as there is an interaction between water and air.

When fish are not getting enough oxygen, they will try to compensate by moving closer to the surface. You might also observe a similar phenomenon when fish tend to stay close to the bubbles of the decorative elements of your stones. Unless it is a surface fish, there is no reason for it to open its mouth to breathe outside of the water.

If this is the case, this means that there is clearly a lack of oxygen that can be explained by injuries, parasites or even certain diseases such as flukes. But if the phenomenon remains global, that is to say if you have a set of fish performing the same modus operandi, then it's a safe bet that the conditions of their habitat are not optimal.

Pay attention to water quality

To remedy this problem, you must start by performing a nitrite test, as well as a water pH test. It is necessary to study the possibility that you have a quality problem with an unsuitable temperature, an incorrect pH level, too much ammonia, nitrates or nitrites.

Thereafter, continue your investigations to understand why your aquarium is lacking in oxygen. Your objective will be to improve the aquatic environment. If you ever have cloudy or polluted water, it could mean that you have poured in way too much food.

Also check that you have no dead fish in your aquarium and if so, consider removing them. Same thing if you have rotting plants. Indeed, these are sources of bacteria that will affect the quality of life of your fish. Either way, remember to replace your aquarium water to achieve a healthy balance.

Investigate the possibility of overcrowding

When you have an aquarium with too many fish, you have natural pollution that sets in, resulting in a low level of oxygen. In addition, bacteria can also grow more easily, but they will be sources of disease.

To avoid this phenomenon, it is important to respect the basic rule, that is to say 4 l per adult fish with a size of 3 cm. This is a general characteristic, because again there are disparities between species that tend to pollute or consume more oxygen.

This is an indicative rule for determining the size of the aquarium and the number of fish. But to refine this result, do not hesitate to do additional research. At the same time, also invest in oxygenating plant species and a bubbler.

A ventilation problem

It is important to have moving water, because it allows to have a better quality water which is explained by the movement of surface water with deep water. As a result, the fish benefit from a better supply of dissolved oxygen.

To achieve this, it is impossible to ignore quality filters allowing the elimination of waste and also excess food. But you should check the filters regularly, because they may have some defects or they need to be replaced.

To bring a greater quantity of oxygen into your aquarium, consider using bubble decorations as is the case with an air stone.

Not only will you enjoy the many benefits of these elements, but you add an extra touch of decoration.

A water temperature that is not suitable for your fish

The water temperature also has its influence on the oxygen concentration. Cold water contains more oxygen than hot water, so be vigilant in hot weather.

If you notice that the temperature of the aquarium tends to rise, you should cool it and if necessary move it if you have direct sunlight. If the temperature is too high for a long period, your fish may not like it because of a drop in dissolved oxygen.