The city's leading expert on aquatic plants says there's a simple way for the water in Lake Wyangan to improve.
Geoffrey Sainty said creating a filter, or natural wetlands, down the eastern length of the lake was an ideal way to address water quality.
"You can manage water bodies if you get water plants growing," he said.
Mr Sainty said the wetlands only had to be five to 10 metres wide, but would run three kilometres along the edge of the lake.
He said it would effectively create a 30,000 square metres of wetlands.
Creating that filter system around the lake would help but Mr Sainty said the turbidity of the water delivered from the Murrumbidgee River meant there was no visibility.
"When you have no visibility, the bacteria grows, so you get toxic blooms of blue-green algae and water plants which used to be there aren't anymore," he said.
"You've got to put natural systems back in."
Mr Sainty said his plan would include delivering water from the Lakeview Branch Canal into wetlands which feed Lake Wyangan.
He said the best people to advise on developing the wetlands would be a ricegrower, as they have plenty of experience creating bays to allow water to flow evenly across land.
"I keep telling people you can't see into the water that's coming into the rice," Mr Sainty said.
"But you can look at the end of the bay and you can just about drink it. Rice is a shallow water plant."
He said ideally it would take one to two days running between 10 to 20 megalitres for the water to progress through a wetland before entering the lake.
While the cause of the fish death event over the weekend hasn't been identified, Mr Sainty said there could be two causes.
The first is water run-off from recent rain collecting residual herbicide from nearby farms which then flowed into the lake.
The second is the turbidity in the channels could have helped stir up sediment in the lake, further reducing the oxygen and light which gets through to the fish.
Mr Sainty believed there was only one word to describe the recent fish death at the lake, mismanagement.
"What you've got to do is get the water plants growing again and they'll do it all for nothing," he said.
Meanwhile, Griffith City Council awarded a tender to create a sediment and nutrient discharge treatment system during the closed section of their Tuesday meeting.
Council has said while that will help improve the quality of the water entering the lake, sediment inflow control was not the only challenge for Lake Wyangan.
"The lake is actually an old quarry and over the decades has accumulated large quantities of sediment loaded with nutrients," Councillor John Dal Broi said.
"The strategy to improve the water quality is also dependent on improving circulation of the water and discouraging the growth of blue-green algae."
Council awarded the tender for the discharge treatment system to Woodlots and Wetlands Pty Ltd.