Locals are being reassured that “thick” green algae that has collected at Dundee’s Swannie Ponds is not harmful to wildlife.
Residents have raised concerns after the green substance appeared in the water at the popular park.
Responding to images posted online, one person wrote: “Remember as kids enjoying the ponds, boats and crazy golf. Such a shame to see it looking like that.”
Another added: “That is disgusting, the city should be taking care of the ponds.”
Others say the ponds should be emptied completely, with the wildlife taken out, and then refilled with water.
But one local councillor says the warm weather and changes to how the water is aerated could be behind the current problem.
Councillor Lynne Short has previously asked people not to feed the swans and other birds.
Dead birds had been found floating in the water, thought to be caused by rotting food.
Ms Short says water at the ponds was previously kept moving and aerated constantly by pumps connected to a nearby reservoir.
However, this process has stopped, and Ms Short has asked the city council to ensure the pumps can be operated manually instead.
She says this could prevent the water from becoming stagnant.
However, it is thought that the recent spell of good sunshine could also be causing problems.
Ms Short said: “If we get the rain and thunder forecast this week, that will help to get the water moving.”
The local authority says a type of algae that can be toxic to animals has not been found in the water.
A Dundee City Council spokesperson said: “Our recent tests at the location have found no blue-green algae present in the ponds.
“We are aware of other vegetation and algae within the pond at this time, however this is found not to be harmful to birds or other wildlife.
“We regularly test the water and will continue to do so. We will also shortly be removing debris and litter from the pond areas, while targeting the current surface algae.”