Oxygen –the elixir of life for your pond

Oxygen deficiency

If fish breathe heavily and hang around under the water surface this can be a sign of oxygen deficiency or a poisoning symptom. Many pond owners think by mistake that the fish are only gasping for breath. But this is not quite correct. They are gasping for the thinner water layer, which is directly situated below the water surface, because this water layer has the highest oxygen content!

By means of an oxygen test ( JBL Oxygen Test O₂ ) you can quickly and easily determine whether there is a problem with oxygen. Only with an oxygen content of below 4 mg/l will you notice a higher breathing activity with most fish. The remedy is quite simple: With the help of aeration pumps and air stones ( JBL PondOxi-Set ) the oxygen content can be significantly raised in just a few hours.

The oxygen content can also be increased by means of a water backflow in the filter. That’s why many pond owners use the water backflow of the filter to operate a watercourse or small waterfalls. Basically the following applies: The more the water surface is moved, the more oxygen can be absorbed. At the same time the following also applies: The warmer the water the less oxygen can be absorbed by the water. That’s why it is especially necessary to aerate in midsummer!

It is, however, more difficult to determine why the oxygen level is so low. Dying organisms (fish, algae, plants) use up quite a lot of oxygen when they are bacterially broken down. Combating algae especially leads to an extreme decline in oxygen levels and this needs to be counteracted at all costs! The symptoms of oxygen deficiency can also indicate nitrite poisoning (see Water tests ).

The water temperature

If you don’t use a pond heater, the water temperature is determined by the ambient air. Depending on the latitude in which you live, there may be strong fluctuations between summer and winter. Pond fish know these water temperatures and can also adapt to them. The water temperatures become critical in midsummer (> 28 ° C) and in deep winter (ice cover). The higher the water temperature, the less oxygen can be absorbed by the water. Therefore, an aeration in the hot summer months is really very useful.

Floating leaves of water lilies cover the surface of the water, reduce the warming caused by solar radiation and thus counteract water heating.

If your pond is deeper than 150 cm, a temperature stratification will occur. In summer the coldest water is towards the bottom and in winter the warmest water (4 ° C) will be right at the bottom. The cause is the negative thermal expansion of the water. Therefore, fish in deep ponds feel more comfortable in extreme temperatures than in shallow ponds. A shallow watercourse can act like a heater in the summer and needs to be shut down in extreme temperatures. Then, however, the oxygen content in the water needs to be increased by other means!

In any case it is important NOT to completely mix the layers of water. The suction inlet for filters or watercourse should NEVER be at the lowest point. You can place the pump on a basket or bucket on the ground. This way the water will not be drawn from the bottom and the pump will not be clogged by leaves so easily.

As just described the water depth is as important In winter. The animals can retreat into the deeper water layers or into the ground (frogs, newts, etc.). There, the water is about 4 ° C and gets colder towards the top until it freezes on the surface. Water is lightest when frozen and this allows it to float on the water. A slight aeration from the middle water layer with the JBL PondOxi-Set in combination with an ice preventer is very useful. It prevents the oxygen level from dropping into potentially dangerous ranges.