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When should I clean out my pond?
Not too often
A well designed and carefully planted pond should not require frequent total clean-outs if properly maintained. Indeed, a complete clean out can often upset the natural balance of the pond and lead to more problems with blanketweed and green water. copyright www.watergardensolutions.co.uk
The need for a full clean out can be reduced by:
- Keeping out excess fallen leaves with a good quality cover net in the autumn
- Prevent soil from washing in at the pool edge
- Trimming back and composting excess plant growth
- Removing and composting invasive plants* © www.watergardensolutions.co.uk
- Removing dead and dying foliage in the autumn. (Tall plant remains can be left until Spring)
- Using a silt digesting treatment if required.
- Maintaining any pond filter as appropriate
- Netting or raking out excessive blanketweed or duckweed growth
- Netting debris off the pool base
As an alternative to a full drain and clean-out, carry out a partial water change:
- Part change the water by pumping or siphoning out water from the base, or from other dirty areas of the pond (anything from 10-60% of the pond volume). You could also use a pond vacuum. If you run the outflow through a net or mesh basket, onto an inconspicuous area of lawn or border, you can look out for and rescue pondlife and return it to the pond.
- Carefully net debris off the pool base.
- Top the pond back up, preferably with rainwater. Alternatively, use tap water with a suitable dechlorinating conditioner. Tapwater can encourage algae growth (See Phosphate issues).
- Split/trim and replant basket-grown waterlilies and marginals in fresh soil every 3-6years/as required
How frequently?
If you’ve carried out regular maintenance, and partial water changes when required, you might never need to completely drain the pond. Otherwise, a complete pond drain and clean-out might be necessary every 5-10 years - generally the longer interval for bigger ponds. Lakes tend to gather silt at about 25mm/1” a year (depending on influx of debris) so a 2m deep lake might reduce to only 30cm water depth after 70 years.
It’s certainly time to clean a small or medium sized pool when the silt depth reaches or exceeds 10-15cm (4-6 inches), or about 25% of the pond depth. In some cases, silt digesting treatments and additional aeration can help to reduce organic silt levels sufficiently to delay a full clean-out,
What time of year?
A general tidy and partial water change could be carried out anytime from Spring to Autumn. The best time for a full clean out is late summer to early autumn. This still gives a month or so for plants and fish to recover before the winter arrives. Spring cleaning tends to be more disruptive to amphibians. Avoid cleaning out during the hottest summer months or in cold weather (below 8-10 deg C). However, if your pond has Great Crested Newts (legally protected) you should leave maintenance to the winter months when they are less likely to be in the pond (Government advice)
See our separate page on How to carry out a full pond drain, clean, and refill?
*Some of the more aggressive invasive plants such as Stonecrop (Crassula) and Water Primrose (Ludwigia), do not compost well, and should be disposed of more cautiously.
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