How to use Coptrol to control Algae in Aquaculture

Algae consume important nutrients and oxygen

|dissolved oxygen|phytoplankton

Free floating and filamentous and blue green algae, (cyanobacteria) are a constant problem in aquatic environments.

In the nutrient rich, oxygenated waters found in aquaculture algal blooms compete with fish and crustacea for:

  • dissolved oxygen
  • nutrients
  • Cyanobacteria dominate phytoplankton competing for available nitrogen
  • Cyanobacteria are able to regulate cell buoyancy and regulate their position in the water column to gain a distinct advantage over other organisms capable of synthesizing their own food from inorganic substances using solar or chemical energy.

View our page “Algae Explained” for more information.

Coptrol more effective and efficient

|copper precipitation|hard water

The use of Coptrol in aquatic environments is a more efficient and effective means of controlling algae than environmentally damaging copper sulphate (bluestone) because:

Coptrol is environmentally friendly. It offers a new approach to the prevention and control of algae in aquaculture.

Coptrol eliminates the problem of copper precipitation in “hard”  water.

Coptrol permits lower concentrations of copper to be  used in algae control.  Because Coptrol does not precipitate in hard water the application rates are less critical.

Coptrol achieves longer copper persistence in water at levels that are toxic to algae.

Coptrol is non-corrosive, non-irritant and easy to use.

Coptrol works in all kinds of water, salt or fresh, hard or soft, turbid or  clear.

Important Safety Principles |water hardness|water temperature|oxygen depletion|

When Coptrol is used, protection from copper toxicity is provided where water hardness is more than 50 ppm (50 mg/litre expressed as calcium-carbonate). Below a level of 50 ppm of hardness, copper in a toxic form may be liberated thus harming fish and crustacea. Water hardness may be tested by using a commercial hardness test kit, or having a small sample (about 250 mL) tested in any NATA registered laboratory.
Water temperature is also important. Below 16°C (61°F) spatiation may occur where copper can separate from the chelating agent, potentially being harmful to fish and crustacea.

Where fish are a valuable resource, it is important to test the water for hardness, and then to test Coptrol application on a few fish before applying Coptrol to the main fish biomass. If water hardness is below 50 ppm or temperature below 16°C (61°F) Coptrol should not be used in the presence of valuable fish and crustacea.

Application to fish impoundments: Decomposing algae that has been treated with Coptrol may lead to oxygen depletion of the water. Lack of oxygen may cause fish to suffocate.

 Therefore, in bodies of water containing fish, it is best to kill algae slowly. It is recommended to treat only one third of the area, then wait 10 days to allow the oxygen level to build up again. Then, resume the treatment beginning from the shore and moving outwards in bands to avoid trapping fish in treated areas.

Effects of copper on fish

A large number of studies have been conducted on the toxicity of copper to fish, whether the copper is naturally occurring or introduced.

Note ‑ the label cautions against the treatment of waters containing trout and other species where water hardness is lower than 50 ppm.

Moore (1984) describes naturally occurring copper in the ionic form as potentially more toxic to fish than any other heavy metal except mercury. However, he notes that copper is much less toxic to fish in waters with a high complexing capacity, such as salt water. He also quotes data to confirm that copper is significantly less toxic to trout in hard waters.

Moore (1984), Stiff (1971) and Pagenkopf (1974) are in general agreement that ionic copper (Cu) and ionised hydroxides (such as CuOH) are the forms of copper most toxic to fish. Coptrol contains copper only in the chelated form, in contrast to copper sulphate which presents copper only in the ionic form.

Stiff (1971) noted that “natural” complexing of copper ions with glycine and humic substances caused some reduction in copper toxicity.

Sprague in 1968 suggested that the chelating agent NTA (nitrilo-triacetic acid) could be used as an anti‑pollutant to protect fish from copper poisoning.

Boyd (1979) reported that chelated copper algaecides are often recommended for application to soft water ponds to prevent copper poisoning in fish. He further noted that “The toxicity of the chelated (copper) compound to fish is less than that of an equal concentration of copper in copper sulphate, so that species with a high susceptibility to copper are not harmed in waters of low alkalinity”. Moore (1984) reported, “In copper polluted fresh waters, a maximum concentration in muscle tissue seldom exceeds 1 mg/kg wet weight. Because muscle residues are generally low; copper does not pose a threat to most fisheries, even those in polluted waters.

Coptrol has been proven to be highly specific to algae and presents minimal risk to fish providing label instructions are followed exactly. Copper in any soluble form is potentially toxic to fish and crustacea. Extreme care should always be exercised in ensuring directions are accurately followed when treating algae infested waters containing fish.

When Coptrol is used, protection from copper toxicity is provided where water hardness is more than 50 ppm. (50 mg/litre calcium carbonate).

If water hardness is below 50ppm, Coptrol use is not recommended.

Shrimp/prawn farms |eel|fish|

Coptrol will eliminate a broad range of algae and control the growth of resistant species.

Coptrol will aid in the cure and control of diseases commonly found in shrimp. These include bacterial and gill diseases, tail ulcers and protozoan infections.

Treat shoreline first to avoid trapping aquatic livestock in shallows.

It is best to treat only 1/3 of the area at a time to avoid oxygen depletion of the water caused by decaying vegetation.

Shrimp, Eel & Fish Dosing Table

Eel Ponds

 Dose of Coptrol


To improve water quality and reduce “off flavour” and lower bacterial/parasitic load.

Use 1.7-2.0 p.p.m. 1.7-2.0 cc (mL) for 1 tonne of water

Dilute the required amount with 10 times the required volume of water. Pour or spray the resultant mixture evenly over the pond. After 2-3 days when algae dies, remove by hand. Repeat every 1-2 weeks.

Fish Ponds

Refer to eel ponds

Do not treat trout with coptrol unless water hardness is more than 50 p.p.m.

Do not use Coptrol in the rare cases where total water hardness (measured in grams of calcium carbonate (CaCO3) is less than 50 p.p.m. Do not treat water if water temp is below 160C (61°F).


Dose of Coptrol


For young shrimp

For young shrimp

To maintain water colour

Use 0.4-0.5 p.p.m equivalent to 0.4-0.5cc(mL) in 1 tonne (1000 litres) of water

If water colour is normal, continue dose after 5-7 days using low dose,frequent application method.

For adult shrimp 

For adult shrimp

To inhibit algal growth

Use 0.85-1.7 p.p.m concentration 0.85-1.7cc(mL) added to 1 tonne (1000 litres) of water.

One application every 1-2 weeks

For young shrimp

For young shrimp

To induce moulting

Use 0.4-0.5 p.p.m equivalent to 0.4-0.5cc(mL) in 1 tonne (1000 litres) of water.

Continue after 5.7 days.

For adult shrimp 

For adult shrimp 

To induce moulting

Use 0.85-1.7 p.p.m concentration 0.85-1.7cc(mL) added to 1 tonne (1000 litres) of water.

One application every 1-2 weeks.

To maintain water quality *reduce off flavour   *Lower bacterial and parasitic loads.

Add 1.8cc(mL) per 1 tonne(1000 litres) of water.

Apply every 30 days as required.

Disease Prevention

Bacterial/Algal disease Including Black Gill and Red Gill disease. Tail Ulcers. Protozoa Infections. Mould Infections

Use.85-1.00 p.p.m. every 1-2 weeks as a preventative measure. .85-1.00 cc (mL) in 1 tonne (1000 litre) of water.

Disease Treatment

Bacterial/Algal disease Including Black Gill and Red Gill disease. Tail Ulcers. Protozoa Infections. Mould Infections

Use 1.7-2.00 p.p.m. 1.7-2.00 cc (mL) for 1 tonne (1000 litres) of water. After 2-3 days use 1-2 p.p.m. concentration again.

When disease is under control revert to prevention concentration of 0.85 p.p.m.

To eliminate heavy filamentous algal infestations such as cladophora, chlorella etc.

Use at a rate of 1.7-2.5 p.p.m. 1.7-2.5 cc (mL) for 1 tonne (1000 litres) of water

Treat 2 or 3 times. When algae starts to die and turns yellow remove by hand.