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Dealing With Silt in Your Pond

By: Dr Gareth Evans - Updated: 6 Dec 2017 | comments*Discuss
Silt Sludge Plant Material Leaves

In nature, ponds are normally a temporary element of the countryside – even if they last for quite some time, they gradually silt up and eventually become dry land; to stay open and attractive features of our gardens, ponds need a little bit of management. Although modern approaches to dealing with blanket weed and green water, such as the now widespread use of ultra-violet clarifiers, have removed one source of silt, the problem still remains and sooner or later, every pond owner is going to have to get to grips with it.

Cutting Out the Sources

Silt is primarily formed from the breakdown of dead plant leaves and similar material at the bottom of the pond – which is one of the reasons that some pond owners refuse to have trees in their gardens. It is possible to combine both, but it does mean that you will have to take the time to make sure that as few leaves as possible end up in the water come the autumn. Covering the pond with netting at this time of year can be a big help towards this, or alternatively you can try routinely raking the floating leaves off the surface.

Water plants themselves are another major contributor – but the good news is that if you keep them regularly trimmed and remove the cuttings, much of the problem can be avoided. However, one source of plant material which is often overlooked is lawn clippings; be careful when you mow around the pond that as little grass as possible ends up in the pond. Aside of adding degradable material, as they break down the clippings can cause havoc with the water chemistry.

Silt Solutions

Digging out the silt from the bottom of the pond used to be a messy, smelly and time-consuming job, but recent developments make it a far less onerous task today. Pond vacuums, in particular, make a lot of routine sludge maintenance very straightforward. There are three main kinds – hand, water-powered and electric – and each has its benefits, although water-powered versions, which attach via a hose pipe to the mains water supply, do not seem to be so commonly seen as either of the other two types.

If you plan to remove the debris on a fairly regular basis then one of either hand-powered or water powered versions could be ideal. They are principally intended to deal with a small amount of silt before it builds up too much and often come with a small brush attachment to allow you to give the pond and ornaments a bit of a gentle scrub to clean them. They can also be useful to remove a quantity of water if you want to do a partial change.

Electric pond vacuums tend to be much more powerful and typically can be used to shift far greater quantities of silt and from greater depths allowing even the deepest parts of the pond to be reached. Like the other versions, they can also be used to remove water for partial changes, or simply to strain out the debris and then return all of the flow to the pond.

However diligently you try, there will always be some silt formed, which will inevitably accumulate – albeit slowly – over the years. To avoid the problem, many pond owners treat their water with a specially formulated mixture of enzymes, bacteria and micro-organisms which break down the silt itself and prevent it building up. There are many varieties available, usually commercially marketed as “silt controllers” or “sludge busters”. If you do use these products, it is important to dose with the right amount – each bottle will state the volume of water it can treat – and use them in accordance with the maker’s instructions to avoid any problems.

Keeping a healthy pond is almost entirely dependent on good routine maintenance and if you can successfully minimise the sources of silt in the first place and keep the water plants trimmed and tidy, it should only really be necessary to clean out the silt every few years. It may not be the most exciting – or pleasant – job that a water gardener will ever be called on to do, but it is an essential one to ensure your pond stays at its best. The results are well worth it.

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I take care of the lawns and pond in a rented holiday home, for the owners. The pond is fairly small (230cm by 110cm and 85cm deep). It is stepped, rather than curved, to the bottom and has eight fish (two about 20cm and six about 10cm and smaller). There are good plants and the water is of good quality. There are aerators installed. The pond continuously silts up to a degree that in the summer, I have to clean out the Cyprio pump every week! I cannot find any advice as to why this is happening. The owner has bought a bigger capacity pump and a large clarifier to aid the smaller one in the pump. Nothing works! Help!
Will - 6-Dec-17 @ 6:28 PM
I bought an Oasis pond vacuum a couple off years ago from PondXpert, it stopped picking up and lost suction recently. I contacted PondXpert and you arranged for a new motor unit to be sent to me by next day delivery and free of charge. I have always been impressed by the very good service I have received at the Billingham store, the staff there are friendly and always helpful and provide sound advice.Please accept my thanks for the excellent service you provide, I cannot fault any of the service I have received, keep up the good work and very many thanks.
ridders53 - 1-Aug-16 @ 8:02 AM
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