If you are planning to or already own a biotope pond or a natural pond you are clearly a fan of unspoiled nature, and want a pond with as little technical equipment as possible and without any exotic animals. While you may not want to intervene when a plant starts to spread, you will still have to carry out a little maintenance. There are, for instance, always the leaves which fall into the water and in the course of time create an increasingly thickening sludge layer. In the wild all ponds silt up eventually.
Of course, you could simply accept this and repeatedly create new ponds in your garden, but nobody wants this! Removing leaves belongs to the key activities in biotope ponds. The jury is out about actively adding fish to biotope ponds, but when fish develop from eggs which have been accidentally imported by birds or plants, this is accepted as a natural process. Biotope ponds often look a little overgrown and wild, but as with gardens, this can add to the charm and may be preferred to a “designer” pond. As biotope ponds often have next to no technical equipment (filters, aeration or watercourse), the construction and shape of the pond is all the more important! The water volume/surface ratio is also vital to ensure there is sufficient oxygen content in the water. A shallow bowl has more oxygen in the water than a saucepan. The biotope pond’s flat areas, where marsh areas form, are especially important if your pond is to work for a long time. Your pond needs a depth of at least 180 cm so that the animals can survive the hard winter. Of course, we are talking about the water depth and not the water plus sludge depth!
One thing you definitely need to deal with is the vegetation around the pond. Most of our trees and bushes lose their foliage in autumn and large quantities of this ends up in the pond. There it sinks to the bottom and forms a layer of sludge. Bacteria decompose the organic matter, consuming enormous amounts of oxygen. This can be so much that the water dwellers may suffer. Preventing leaves from entering the water is the best method, removing them is the second best method. Otherwise we are quickly back at the subject of “sedimentation”.