Find out how to gently clean your garden pond in July. Step-by-step guide to nutrient reduction for a stable biological balance.
In midsummer, biological activity in garden ponds reaches its peak. When organic material—such as dying algae or wind-blown pollen—sinks, microorganisms decompose it at the bottom. This process consumes significant amounts of oxygen. If the pond has too much sludge, there is a risk of oxygen deficit during high water temperatures, which is life-threatening for aquatic creatures such as the common hawker dragonfly (Aeshna juncea) or the smooth newt (Lissotriton vulgaris). Careful cleaning therefore serves as active risk prevention.
| Observation | Cause | Action |
|---|---|---|
| Sudden cloudiness | Algal die-off | Reduce nutrient excess |
| Foul smell | Anaerobic decomposition | Carefully remove sludge |
| Gas bubbles rising | Methane formation | Targeted desilting |
Preparation: Work exclusively in the cooler morning hours. Have collection containers ready to move removed sludge directly to adjacent garden beds; it acts as an organic fertiliser there.
Selective desilting: Never remove all sediment in one go. Work in sections so as not to endanger the microfauna—such as the backswimmer (Notonecta glauca). Use a fine-mesh net or a special pond sludge vacuum bell.
Bank maintenance: Remove dead plant parts from native reed species like the lesser bulrush (Typha angustifolia) before they sink completely. Take care not to remove egg clutches from water insects.
Follow-up check: Observe the behaviour of the pond inhabitants. If animals like the swan mussel (Anodonta cygnea) move towards the surface, the procedure has been too intensive and must be stopped immediately.
Strictly avoid the use of chemical algaecides. These permanently disrupt the sensitive metabolism of the water body. Mechanical cleaning using pump vacuums should also be avoided, as this inevitably kills microorganisms like water fleas (Daphnia magna) and aquatic larval stages. Focus on manually removing the bottom substrate.
A natural pond regulates itself to a large extent if there is sufficient plant density (about 50-70% of the area). The goal of this measure is merely to keep the artificially accelerated process of silting up, known as succession, on the desired track to ensure a permanent habitat for native amphibians and insects.
Early morning hours on overcast days are ideal to expose the animals to minimal stress at lower temperatures.
Yes, pond sludge is an excellent organic fertiliser. It can be spread thinly on beds or mixed into the compost.
Remove a maximum of one third of the deposits per session to maintain the habitat for microorganisms and larvae.
Main article: Nature garden in July: How to manage succession and pond ecology
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All species data comes from scientific sources (CC BY 4.0 / CC0). Attribution according to licence terms. Complete source overview →