Pond sludge treatment

Written by cullend
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Pond sludge treatment
Ponds benefit from sludge treatment. (pond image by Tomasz Kubis from Fotolia.com)

As ponds age, they develop muck, or sludge, layers that grow thicker over time. Organic material like plants and fish waste accumulate on the bottom of the pond in addition to normal rainwash that brings sediment from your watershed. Though muck is a natural byproduct of an aquatic ecosystem, it can become a problem as it begins to decrease the depth of your pond. Several treatments exist to reduce and prevent future muck accumulation.

Bacterial Supplement

Bacteria are microscopic autotrophs that naturally inhabit ponds and break down all organic material that makes its way into the pond. However, their populations are a function of how much detritus is actually available, which may or may not be large enough for them to work efficiently and quickly. In this case, bacterial supplements serve to spike the bacterial population in a pond and increase the speed at which muck is broken down. Bacterial products are available specifically for lakes and ponds and typically require an elevated initial dose, followed by weekly doses so long as temperatures are above 20 degrees Celsius. Microbe Lift and BactaPur are popular choices.

Pond sludge treatment
Bacterial specimen. (bacteria image by chrisharvey from Fotolia.com)


Aeration is the best long-term solution to break down muck and prevent further accumulation. Bottom-based aeration systems include a bottom-mounted manifold that diffuses compressed air to circulate the entire pond volume. This creates an even distribution of oxygen throughout the pond all the way down to the sediment-water interface, or bottom of the pond. Normally, ponds are anoxic, or devoid of oxygen, at the bottom, and only anaerobic bacteria can survive. However, when oxygen is present, aerobic bacteria, or oxygen-utilising bacteria, can establish a population. Aerobic bacteria are several times more efficient than anaerobic bacteria. Installing a bottom-based aeration system before you apply bacteria supplements can aid in increased muck reduction.


Dredging should be considered as a last resort as it is expensive compared to other treatment options. Dredging involves large equipment designed to till or loosen the bottom sediment with a large cutter head. As the sediment is loosened, a pump draws it up through a pipe and delivers it to a different location. Dredging usually costs about £6 per cubic yard of relocated sediment.

Draining and Excavating

If it's possible, consider draining your pond and hiring an excavation company to dig out the pond again. Aside from dredging, this is the quickest way to remove sludge from the bottom of your pond. However, the inherent consequence of losing fish and wildlife make this option prohibitive for most pond owners.

Pond sludge treatment
Excavator. (Hydraulic excavator at work. Shovel bucket against blue sky image by Andrei Merkulov from Fotolia.com)


If a pond is allowed to continue to accumulate sludge and muck, more and more organic material settles to the bottom and begins decomposition. Bacteria begin to break down the material but in doing so re-release the nutrients bound up in the plants and animal waste. Phosphorus is the key nutrient in this case and the primary fuel for algae blooms. Algae can easily choke a pond and create oxygen depletion and an unsightly mess. Additionally, a rising muck layer serves to decrease the depth of your pond, adding to its susceptibility for algae blooms and low oxygen problems.

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