Biological Fundamentals

Introduction

Garden ponds are enjoying increasing popularity. They enhance garden architecture and offer numerous life forms a new habitat in and on the water. Thus garden pond owners not only add to the visual beauty of the garden they also create an ecological niche for many animals and plants. Also various ornamental fish, such as gold fish or colourful koi, are kept in the garden pond. There are garden ponds in all conceivable shapes and sizes. Smaller ponds are often installed as prefabricated ponds, larger ponds are usually installed as lined ponds or natural ponds with a clay seal. The deepest point is usually extended to a frost-protected depth of more than 100 cm. Koi ponds should have a minimum water depth of 1.50 m. Oase offers an extensive pond construction product range.

A stable biological balance exists in natural, healthy bodies of water. Different plants, plankton, fish and microorganisms are interdependent via the so-called food chain. Any outside intervention that affects specific members of the community, over time will affect all life forms in this ecosystem. A natural ecosystem is capable of accommodating disturbances within certain limits. Artificial eco systems, such as garden ponds with fish stock, can become permanently unbalanced biologically even through small disturbances.

Most problems in a garden ponds can be attributed to over-fertilisation due to a high level of fish stock and feeding the fish. Because of the small size of garden ponds, excess fish food and fish excreta cannot be sustainably decomposed without external help. Through the artificial supply of nutrients man has intervened in the biological balance. The resulting condition of overfertilisation, (also referred to as eutrophication by specialists) results in algae bloom with pea-green water, which in the truest sense of the word, clouds the garden pond owner's satisfaction.

Initially this does not have a negative effect on the life forms in the pond. While they are growing during the day algae produce oxygen that is given off in the water. At night algae and plants consume oxygen and give off carbon dioxide into the water. After a period of several days to several weeks the algae dies and drops to the floor of the pond. On the way to the base of the pond, and on the base of the pond itself, plankton and microorganisms (bacteria and fungi) metabolise the algae. These organisms re-constitute only a small portion of the nutrients, nitrogen and phosphate, (N and P) in their own biomass, the rest is given off to the surrounding water. This excess phosphate can be effectively removed through the use of Oase Phosless cartridges. The entire decomposition process is referred to as mineralisation.

However mineralisation consumes the same amount of oxygen that the algae previously produced. Oxygen content in the water is rapidly reduced so that fish and other water organisms suffocate. At this point your garden pond is in a state from which it can no longer free itself with its own energy.

To prevent insufficient oxygen, circulation pumps or fountain pumps and filter systems are used to enrich the water with oxygen. The stagnant water of the pond is changed to "stagnant flowing water" through water circulation. This enables a constant exchange of gas in stagnant pond water which makes a significantly increased self-cleaning effect possible. The specific factors that cause this process and further this process and the function of modern pond filters are described below.