Tips For Cleaning Out A Pond

Late autumn is an ideal time of year to clean out your pond, before frogs and other wildlife return to spawn. You will also be causing the least disruption to your pond plants. The extent of the cleaning required will depend on the overall condition of the pond. Here is an overview of how to clean your pond ready for the spring.

If the pond is neglected and overgrown, and it has been several years since it had much TLC, you may need to almost completely drain the pond. On the other hand, if you have made a reasonable effort to maintain your pond, it is probably best to clean the pond without draining it.

An overgrown pond is not only an eyesore, but it will also be likely to have low oxygen levels, which makes it harder for fish, plants, and other aquatic life to thrive. The size of the pond also affects how quickly it becomes affected by rotting vegetation, debris, and so on. Smaller ponds need more regular cleaning than larger ones.

Cleaning out a polluted pond

If the pond water looks cloudy, and you notice a bad smell if you disturb the rotting vegetation on the bottom of the pond, it is likely that the water is stagnant and has a poor nutrient balance. In this case, it’s easiest to drain most of the water.

The first step is to find a suitable container to transfer any plants and creatures into whilst you carry out the clean. The marginal plants, which live on the shelves around the edge of the pond, can happily survive out of the water for as long as you need as long as they are kept damp.

Deep water plants such as Water lilies, Amphibious bistort and Water hawthorn will be ok for a few hours in the shade, but any longer and ideally they should be under water in a bucket or other container.  Any submerged oxygenators should be kept in water, though if needs must they could be kept in a plastic bag or bin liner for a few hours or even overnight as long as they are not allowed to dry out.

It is easiest to drain the pond with a pump, which you can hire for the day if you don’t have your own. A small pond might be emptied with buckets and a few pairs of helping hands in an hour or two. Take care to remove any creatures and plants and transfer to the holding tank as you go along.

Dead or decaying vegetation which you intend to discard should be left on the side of the pond for a few hours, to give any sheltering wildlife the chance to return to the pond. The silt and rotting debris on the bottom of the pond can be scooped out with a spade, bucket or trowel, and recycled in the garden if you wish.  Be careful not to damage the pond liner.

It’s recommended to retain a small amount of the silt, unless the pond has been heavily polluted with chemicals or oils. This is because it will contain some nutrients, bacteria and other microscopic pond life which will help rebalance the ecosystem of the pond more quickly when you fill it. You may also choose to retain some of the water for this purpose.

Do not be tempted to scrub the dirt or slime off the liner of the pond or any rocks or stones in the pond as you are just making work for yourself, and this natural biofilm supports billions of microbes which help to keep the pond healthy and clean. Return any silt and water you want to retain to the pond, and position the deep water pond plants which are grounded at the base of the pond.

It’s best to refill the pond with rainwater collected in a water butt if possible, so try and have one in place during the weeks leading up to your clean out. If this is not possible, let any tap water stand for a 24 hours before adding the creatures and plants back to your pond.

Remember that completely changing the water in your pond will mean that the ecosystem will take several months to re-establish itself. It’s important therefore to have the right balance of plants to oxygenate the water and build up nutrient levels, and inhibit algae growth.

Look for a mixture of hardy submerged plants such as Hornwort, Willow moss and Water crowfoot.  Floating plants such as Water lilies, Amphibious bistort or Frogbit are important to provide shade and shelter, and marginals such as Water forget-me-not, Creeping jenny and Lesser spearwort are good choices to place on the shallower ledges around the edge of the pond.

Cleaning a pond without draining it

If the water is reasonably clear, then you are best to avoid changing the water. Remove any floating debris with a net or garden rake, and cut back any decaying plants above the water line.   Some reeds, rushes and grasses have quite interesting winter foliage even when dead, so you may choose to leave cutting these back until late winter or early spring -just be careful not to chop back any new season’s growth.

If your pond suffers from Duckweed, remove as much as possible with a fine sieve as any that remains will die back and spores will over-winter in pond ready to grow again in the spring. Remember that in the autumn, brown plants are not dead and will regenerate in spring, so don’t throw them out.

If the sediment at the bottom of the pond is foul smelling, scoop most of it out with a fine net or a pond vacuum. Thin out any pond plants which have become overgrown, so that around two third of the pond surface is visible, and the water does not look soupy. Finally top up the water if necessary.