For myriad reasons it is inevitable that pond water will not stay clear or clean.
Algae is the most common presence in a dirty pond, turning the pond an undesirable blue green colour. Algae growth occurs for a multitude of reasons:
- Sunlight: Light is needed for all plant growth, algae is no different. In the warmer months, the increased water temperature aids in algae growth. Shallow ponds allow more light in, increasing algae growth.
- Fish: Overstocking of fish causes more fish waste, increasing the nutrient levels. High nutrient levels increases algae growth.
- Lack of/No water circulation: Without water circulation, algae can grow unhindered.
- Debris falling in the water such as leaves and animal or bird droppings will become nutrient which will feed algae growth.
There are a variety of solutions for keeping pond water clean. Some ponds in time can achieve a “balance” with the use of water movement, plants, ideal water depth, areas of shade, oxygenation, wildlife etc however these environments are sizable enough to replicate nature and are far removed from the ornamental pond you are are trying to keep clear and clean.
One defence against algae growth is a biological filter.
A biological filter in a unit fitted to the pump inlet which not only has a more comprehensive filter pad, but includes a chamber where bacteria will develop which will consume the algae which is messing up your water. The very effective defence against algae growth is Ultra Violet Light. Water passes over an illuminated Ultra Violet lamp killing the algae spores resulting in crystal clear water (although algae can remain on walls and rocks). Many products on the market will include both biological filtration and UV Clarification. These are a pressurised sealed unit installed above water level or perhaps outside the pond in an adjacent garden. A pipe would deliver water from the pump to the unit, and a further pipe would deliver the treated water back to the pond.
Units are also available complete with pump/bioligical/uv clarifier all together. It is worth noting that Ultra Violet Lamps require replacing every 12 months. Pressure Filters or Gravity Fed Filters are the most common types of biological filters. They both require pumps to feed the water to the filter. The size of the pump and filter is detemined by the size of the pond. Clearpond have a good tool on their website, helping you determine the size of your pond: https://www.clearpond.com.au/how-to/online-calculators/pond-volume
For smaller water features, even containing fish and plants, pond treatments & additives are readily available in liquid and powder form depending on the water problem. These additives will be ongoing and are generally very effective. Periodic water replacement will be required. Barley Straw is a common and effiective algae growth inhibitor.
A pond pump is an excellent way to get your water circulating. It is a common belief that a pond pump and it’s inbuilt filter pad will keep water clean. This is not accurate. The filter pad in a common pond pump is present to fitler the debris andprotect the pump from damage.
Shade can help lessen the impact of direct sunlight on a pond. The ideal time to create your pond is during construction of your house, but may not be in the forefront of most homeowners minds. Aquatic Plants such as lily pads can create shade as well.
– Aki Iyer
