The first of 16 machines aimed at keeping vital fish stocks alive in NSW's ailing rivers will be installed as soon as Wednesday as fears build of more large die-offs amid searing inland temperatures.

The Department of Primary Industries is dealing with eight fish kill or algal bloom alerts across the state.

The solar-powered aerators will bring much-needed oxygen to pockets of the hypoxic waters of Darling River at Menindee, the Keepit Dam near Tamworth, the Burrendong Dam near Dubbo and other sites.

Inland NSW and Victoria roasted on Tuesday, with days more of the extreme weather to come. Tolarno station on the lower Darling had dust devils to add to the heat. Credit:Dean Sewell

The first of the devices, which can raise dissolved oxygen levels over an area about the size of a basketball court, will go into Pooncarrie on the lower Darling not far from where up to a million fish died earlier this month near Menindee. Silver perch, Macquarie perch and Murray cod will be among targeted species.