Is your pond filled with sludge?
The article concerns the question – Is your pond filled with sludge? In previous columns we have discussed how to get pond water clear and healthy by using ultra violet clarifiers and by using filtration systems. Once the water in a pond becomes clear, you can of course see the bottom of the pond, unfortunately we do not always like what we see. Usually the bottom of a pond is filled with sediment and sludge and this accumulates for two reasons. The first is the breakdown of organic matter in the pond. This matter includes fish poo, plants, leaves and even dust and soils from the garden.
The second reason that sludge builds up in the bottom of a pond is due to the constant renewal of bacteria. Some of these bacteria assist in breaking down the waste that is produced by the fish, which if left in the water can cause algae blooms. As these bacteria grow and reproduce they produce a slimy secretion which attracts and traps small particles of waste that settle on the bottom as layers of sludge.
Small amounts of this sludge up to say 2cm in thickness will not cause any undue harm to fish or frogs. However, if this waste is left to build up over and above 2cm, it can allow the production of undesirable gases to occur and can cause a proliferation of disease causing bacteria in the pond that can be harmful to fish.
There are several ways that this waste can be removed from the pond. The most common method used by people is to completely drain the pond. This method concerns me as aside from removing the waste from the pond, many of the beneficial bacteria that assist in keeping the pond clear and the fish healthy are removed in this process.
The best way of removing this waste is to siphon it out. You could use a piece of hose for this but as many ponds are in the ground it can difficult to get enough fall for a siphon to work. There are pond vacuum cleaners, such as “Pondovac”, that can draw this waste out of the pond and the waste water can be distributed over the garden. The top of the line models can also remove hair algae, leaves and other small debris as well as the sludge and if you can use a household vacuum then you’ll be able to use a pond vacuum.
Once the waste is removed, you can add one of the waste digesting bacteria products to assist in slowing down the build up of it in the future. These products contain bacteria that actually consume much of this waste before it has a chance to settle as sludge and they assist in improving water clarity in the pond. As these are natural products they are completely safe for your fish, even if accidentally used in excess. These products can be added weekly during the warmer months of spring and summer and monthly during the cooler months of autumn and winter.