Hydrogen peroxide is being tipped into Adelaide's River Torrens to help prevent toxic blue-green algal blooms.

Half a tonne of powdered chemical has been mixed with liquid and poured into the waterway between Adelaide Zoo and the University footbridge in the city, with researchers saying the quantity is too small to pose a risk to fish or birds.

The health of snails and freshwater shrimp will also be monitored during the treatment.

Steven Gatti, from Natural Resources Adelaide and Mount Lofty Ranges, said hydrogen peroxide was known to be effective.

"It kills the blue-green algae at the concentration we're delivering today, so it's really just about confidence in delivery in years to come," he said.

"Peroxide is a completely natural chemical; it breaks down to water and oxygen after around 24 hours."

"The mouthwash you might use in the morning is 1.5 per cent peroxide — we're applying 0.0005 per cent peroxide."

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Outbreaks of blue-green algae during Adelaide's hot, dry summers have led to several closures of the Torrens to water-based activities in recent years.

Mr Gatti said a near-record wet summer for Adelaide had prevented any algal outbreaks this year.

"Whilst we don't have any blue-green algae this year, the test is really about logistics; how we take the amount of hydrogen peroxide we want to apply and apply it in a safe manner," he said.

The researchers said the Torrens was generally quite a healthy waterway compared with those in other major Australian cities.

One of the river's biggest problems had nothing to do with algae — in early 2009 the weir which dams the city section of the Torrens to form a lake malfunctioned.

A gate partially opened due to an electrical fault and much of the water drained away to leave a muddy mess in late summer, just as Adelaide's busy festivals season was about to get underway.