ACT government officials say it could take a decade to rid the territory's lakes of blue-green algae, nearly 30 years after it first appeared in Lake Tuggeranong and more than 40 since it turned up in Lake Burley Griffin.
Preliminary test results, presented to water quality bosses in mid-June, identified no clear front-runner among four solutions trialed to kill off the "cyanobacteria" in Lake Tuggeranong, lead University of Canberra researcher Dr Fiona Dyer said.
The $93.5 million ACT Healthy Waterways project, which backed the research, wraps up officially on Sunday; but leftover funding will be used to test more products over the next 12 months, and monitor plants in rain gardens and wetlands over two years.
"I think Canberrans are starting to become aware that this is not [going to be] a short-term, easy solution," Dr Dyer said.
"But I think we are getting closer to being able to identify what the key things are that need to be done, then it becomes a choice as to how much money we're prepared to spend on it."
Of the solutions trialed from January to April this year, peroxide gave the algae a "super short knock-down", but another treatment, Diatomix, showed no effect under the harsh summer conditions.
Phoslock, a clay that binds the algae-enabler phosphorous, proved it was able to do so; but five times the pollutants held in Lake Tuggeranong's sediment were coming in from stormwater drains, Dr Dyer said.
"That's going to take a long time to deal with and [need] significant, ongoing investment," she said.
"I kind of liken it to vacuuming your house; you don't [do it] once and think it's done forever."
A significant portion of the five-year-long healthy waterways project was dedicated to educating Canberrans about stormwater pollution, program manager Ralph Ogden said.
Surveys handed out at the Royal Canberra Show and the National Multicultural Festival found about 60 per cent of people had heard of the H20K education campaign, and 20 to 25 per cent had changed their behaviours.
Dr Dyer previously said her team had found several dead cats in Tuggeranong's stormwater drains. She suspected they had been dumped there by people who didn't want them.
"For a campaign that was only one year and a half old at that stage, that's pretty good - that's very good, actually," Mr Ogden said.
"But it also highlights it's not 100 per cent of Canberrans who got the message, so we have more work to do in that area."
The ACT government would press on with public education through its employed public education officer, Mr Odgen said. Healthy waterway's 20 new rain gardens, wetlands and ponds across the territory - including $30.2 million worth for Tuggeranong - would start to have an immediate filtration effect.
It would take about two years before they were working to their full capability, but by the time Canberrans changed their behaviours to limit pollutants, and a trialed, checked, treatment was put in place across the whole of Lake Tuggeranong, it would be about 10 years, Mr Ogden said.
"I think that's a realistic timeframe," he said.
"These are big, complex problems that affect large areas."
ACT director of water catchment and policy Matt Kendall said the National Capital Authority, which manages Lake Burley Griffin, would likely be looking over its shoulders to see if a potential blue-green algae solution was transferable to that lake.
"Lake Tuggeranong is the location where the issues are the greatest so it makes sense to go there first," he said.
"Lake Burley Griffin is about 10 times the size in terms of the volumes."
Blue-green algae exposure can cause skin irritation, flu-like symptoms and gastrointestinal illness. At its worst, it can make neurotoxins that destroy nerve tissue and are potentially deadly to animals and humans.