How to use Coptrol to kill Algae in Waterways and Irrigation Channels

Algae in irrigation channels a persistent problem!

There are more than 17000 kilometres of earthen irrigation channels in Australia all with varying amounts of plant life and weed growth on the banks and in the water way. Decayed vegetation from nearby trees and decayed foliage from the channel banks as well as the run off from adjacent farms provides plenty of aquatic nutrients. When combined with abundant sunlight and high summer temperatures, blooms of algae are a frequent occurrence.

Algae and Algal blooms

There is no easy definition of an alga. Algae are generally microscopic organisms, are generally thought of as simple aquatic plants which do not have roots, stems or leaves and have primitive methods of reproduction.
Algae can impede water flow, create an environmental nuisance and may even be toxic to humans and stock.  Successful eradication of algae depends on the correct identification of the species, and the use of an algaecide that does not harm aquatic animals, livestock, plants, humans and is specific to algae and no other plant life.
Coptrol is a chelated copper compound with a low level of toxicity. Its unique ability to kill algae is because algae actively seek out Coptrol for its nutrient value and they absorb it through their cell walls. Digestive enzymes within the algae cell break down Coptrol which releases the copper held inside the chelate. Because the algae cells gradually accumulate Coptrol, there is not  an immediate toxic effect on algal cells. Generally it takes between 36 to 48 hours for results to become apparent. This rate of deterioration is dependent on the dose rate used and level of algal concentration at the time of application.

What are the dosing options?

Dosage rates depend on a number of factors including water volume, flow rates, algal concentration and dosage methods.

There are three practical options available:

  • Single dose point
  • Multiple dose point
  • Drip/spray application

We do not recommend the use of Coptrol if the single dose option is chosen.

Multi dose point method

The multi point method is used when there are relatively rapid flow rates of water. Subject to being able to apply the product in a uniform and reliable manner, the rate of application should be 2ml per 1000L (cubic metre) of water continuously for 48-36 hours.

It should be noted each system has different characteristics which may influence the efficiency of this dosage recommendation. For example undertaking multi point dosing after the accumulation of high levels of algae have occurred will significantly reduce the effectiveness of this type of application and may require higher application rates over a longer period.


This method is dependent on the ability of the operator to be able to pass sufficient Coptrol over the surface of the water in the channel. This approach is only feasible with either a static or slow moving channel system and requires the operator to be able to apply Coptrol evenly over the surface of a channel. In our experience this system is more cost effective and reliable than the multi point dose method and can be used to prevent and treat problem algal developments. The suggested rate of application in this situation is 5ml per 1000L (cubic metre)of water. This will require a minimum of 48-36 hours contact time. In extreme conditions rates can be increased to 10ml per 1000L (cubic metre) of water.

Recommended dose rates
If algae is a problem  in a waterway or irrigation channel, follow this 5 step method to keep your waters clear and bright.

1.  First identify the algae present. Please use our guide here for more information. This page explains common algae within Australia.

2.  Now calculate the volume of water to treat. Ignore depths below 1 metre. Please refer to our “Quantities” page to calculate the amount of water to treat.

3. Next calculate the amount of Coptrol needed. An easy way to calculate is:

• If the algae is fine and free floating use 2 mL of Coptrol per 1000 Litres (1 cubic metre) of water. That is equivalent to 2 Litres of Coptrol per 1000 square metres of surface area.

• If the algae is long and stringy use 5 mL per 1000 litres of water (1 cubic metre) or 5 Litres per 1000 square metres of surface area.

4. Dilute the required amount of Coptrol using a 1:10 or even a 1:20 Coptrol water dilution.

5. The best application method is by spraying. Apply on a sunlit wind free day when algae first appear. If this is impractical, please refer to our Application” page on how to apply Coptrol.

There are advantages and disadvantages with both methods of application, on balance we have found the drip spray method to be most efficient.