Coccolite chalk is a porous chalk (calcium carbonate) that consists of fossil skeletons of dead algae that accumulated millions of years ago on the bottom of the seas.
1 gram of coccolite chalk has a surface of no less than 2,5 m².
Many ponds have a sludge layer that continues to grow over the years. This growth occurs through organic substances such as leaves, algae, high fish stocks, etc.
The organic material that ends up in the water then sinks to the bottom. When the self-cleaning capacity of the water is exceeded, the degradation of the sludge is smaller compared to the growth. In this way, annual sludge will be added if no action is taken.
A thicker layer of sludge not only ensures that the water becomes increasingly shallower, but also that such a layer of sludge represents a real danger to the fish life present. This sludge layer contains many gases that are created by fermenting the organic fraction in the sludge. Gases such as methane and hydrogen sulphide are accumulated in the sludge sediment and are fatal to the fish stocks present.
Coccolite chalk can be used on almost any pond. This applies to ponds with a (thick) sludge layer as well as ponds without a sludge layer. The formation of sludge can then be prevented on ponds without a sludge layer. It must be borne in mind that a newly constructed pond also receives a quantity of organic material every year.
The coccolite chalk is evenly distributed on the pond with a spade or shovel. You can use a boat on larger ponds to increase the range. The coccolite chalk will float in the water for a while (called a suspension) and, depending on the water temperature, will sink to the bottom in a few days. In this way the chalk is evenly distributed over the bottom where it has its effect.
The large surface of the coccolite chalk has its specific properties. This surface is needed so that bacteria can settle on the chalk after dosing on the pond. These good bacteria will in turn ensure that the existing mud layer is broken down. In this way one can keep the pond healthy. Coccolite chalk can penetrate the bottom layer up to 15 cm.
The chalk therefore acts as a medium for the bacteria that break down the mud layer. The very low solubility (0,96%) also ensures that the substrate remains intact. The pH of the soil is slightly increased so that a more suitable environment for the bacteria is created.
The intended bacterial culture is aerobic. This means that they need oxygen to survive. Oxygen is therefore an important parameter for proper functioning. There is usually enough oxygen present on the average fishing pond. However, if a pond with a historically thick organic sludge layer and a limited water column is available, some caution is required. If the bacteria were to develop massively as the water warmed up, the oxygen level could drop. A aerator can provide a solution here.
On the other hand, the coccolite chalk ensures that the water becomes clearer because the chalk forms a bond with floating particles in the water. In this way the underwater plants also have a better chance of development as the light penetrates deeper into the water.
Time of application:
Coccolite chalk is used in the spring when the water temperature is between 10 and 12 °C. In normal years this is March-April. The oxygen balance of the water is ideal at these temperatures.
The positive effects of using coccolite chalk are enormous. In addition to reducing the sludge layer present, fermentation and the formation of gases in the soil are also avoided. The oxygen level has a more stable and higher curve during the year. In addition, the chance of algal blooms is lower due to the binding of nutrients to the chalk and the faster speed of the processes.