These single-celled organisms live in fresh, brackish (combined salt and fresh water), and marine water. These organisms use sunlight to make their own food. In warm, nutrient-rich (high in phosphorus and nitrogen) environments, cyanobacteria can multiply quickly, creating blooms that spread across the water’s surface. The blooms might become visible.

Cyanobacteria blooms can start to multiply very quickly. Blooms can form in warm, slow-moving waters that are rich in nutrients from sources such as fertiliser runoff or septic tank overflows. Cyanobacteria blooms need nutrients to survive. The blooms can form at any time, but most often form in late summer or early Autumn.

How can you identify it?

You might or might not be able to see cyanobacteria blooms. They sometimes stay below the water’s surface, and sometimes float to the surface. Some cyanobacteria blooms can look like foam, scum, or mats, particularly when the wind blows them toward a shoreline. The blooms can be blue, bright green, brown, or red. Blooms sometimes look like paint floating on the water’s surface. As cyanobacteria in a bloom die, the water may smell bad, similar to rotting plants.


1. Introduce pond aeration and water movement through aerators or fountains. Find out more here.

2. Pick up and dispose of pet waste, a common source of excess nutrients and bacteria.

3. Implement landscaping strategies,

4. Incorporate native vegetation, rather than cement banking or manicured lawns, around pond and lake banks. Allow natural vegetation to grow near the water’s edge.

5. Ask your lawn-care company to remove grass clippings and leaves to prevent decomposition in or around ponds and lakes.

6. Use phosphorus-free fertilizers and detergents to limit nutrient-rich runoff.

7. Have a pond management professional apply phosphorous-binding products, which prevent nutrients from stimulating algae growth, in nutrient heavy lakes and ponds.

8. Consult a qualified water-management professional who can monitor the water quality regularly and advise appropriate treatments.

9. Add Phoslock – Phoslock is a product designed for phosphate removal from water. Its active component is lanthanum which reacts with phosphate forming an insoluble and biologically inert compound. Its ability to bind phosphate makes it an effective tool in lake restoration.

Phoslock was developed in Australia by the CSIRO as a way of utilising the ability of lanthanum to bind phosphate but at the same time making it safe for use in natural aquatic systems.When used in lake restoration, Phoslock is usually added to the lake as a slurry. As this sinks through the water column it binds phosphate as it goes. Once settled on the sediment it can continue to bind phosphate released from the sediment, thus controlling one of the major blocks to lake restoration – sediment phosphorus release.

The ability of Phoslock to bind phosphate is important because phosphate is the form of phosphorus which is biologically available and used by plants – especially algae in lakes, to promote growth. Excessive amounts of phosphate entering water courses is one of the main causes of deterioration of water quality in freshwaters today because of the way it drives algal productivity and undesirable changes in the balance of aquatic life. The process is known as eutrophication.

The ability to remove biologically available phosphorus in a lake is therefore a major step towards improving water quality. Phoslock can be used in lakes and ponds as well as other standing waters (e.g. reservoirs, fish hatcheries) where high phosphate levels are causing problems. It is not usually applied to flowing waters. Click here to read more.