The action comes in the wake of the Menindee fish kill, which was triggered by a sudden drop of temperatures after a severe heatwave nudged the mercury to 46 degrees.

Dying blue-green algae resulted in further drops of already low dissolved oxygen levels, pushing many thousands of fish beyond their tolerance levels.

Primary Industries Minister Niall Blair said nine of the machines will be installed “as a temporary measure” to help fish populations survive the brutal combination of low river flows, algal blooms and severe heatwaves.

Three of the nine machines being trucked across the country from Western Australia will go to Burrendong on the Macquarie River, where the perch are at risk, Mr Blair said.

Four others will be installed on the Darling River, including near Menindee, site of last week's massive die-off that killed as many as a million fish. These included endangered silver perch, as well as golden perch and giant Murray cod, some of which were decades old.

The remaining two will be deployed at Keepit Dam in northern NSW.

“We're not going to die wondering - we're trying to find a solution,” Mr Blair said.

Each solar-powered aerator should be able to boost oxygen levels over an area about the size of a basketball court.

“It's not a silver bullet” but it could keep some pockets of fish alive, he said.

Mr Blair said his department would look at adding enclosures to prevent poaching by anglers drawn to the remaining healthy fish stocks.

Richard Kingsford, director of Centre for Ecosystem Science at University of NSW, said that aerators are routinely used on dams supplying water to communities.

MAP: Where is Lake Burrendong …

“It's a band-aid,” Professor Kingsford said.

“They'll do a little bit for a little while. It still leaves a lot of river that's been affected.”

Labor's water spokesman Chris Minns said the problems are likely to repeat unless flows are restored.

“If the NSW government refuses to focus on returning low and medium flows to the river it doesn’t matter how many fish they return to the Darling this environmental disaster will happen again,” Mr Minns said.

“It’s time [Minister] Blair acknowledged this disaster is as a result of his mismanagement of the waterway and start returning flows to the Darling,” he said.

“Anything else is a distraction.”

Areas of immediate worry for more fish kills include the Murrumbidgee River and even the Murray River, although the extent of the problems mean “we're concerned pretty much everywhere”, he said.