More than 400,000 megalitres of water has been pumped down the Murray River to stop toxic blue-green algae killing aquatic life.
The algal bloom has spread over 500km and forced water to be turned off in some towns. Victorian Water Minister Lisa Neville said there is no quick fix to the algae problem.
"What we really need is some significant rain," Ms Neville told reporters.
"Or we need to wait until the temperatures cool in the north."
The Commonwealth Environmental Water Holdings has sent 400,000 megalitres of water through the Murray in a bid to move the algae along, but this isn't flushing the algae out.
"All that will do is stop the water stagnating and becoming black water," Ms Neville said.
"We don't want it to become black water and therefore unable to sustain fish and other life in that river."
Towns along the Murray have had their water turned off due to the toxic algae, but Ms Neville said those customers had been reconnected. Ms Neville said tap water is safe to drink, but swimming is unsafe.
"It does look very attractive on hot days, but it can cause skin rashes and itchiness and other conditions."