The reason why a remains unknown despite the water being tested by officials.
Residents have been left concerned after the water in Mina Road Park abruptly changed colour on Monday afternoon (afternoon 25).
People living nearby say this is a regular occurrence and are concerned that such pollution could have an impact on local wildlife.
The BBC has also reported that a pet owner claimed his dog fell ill and started vomiting bile after drinking from the stream.
Molly Gilbert, who lives next to the stream, said: "It's horrible and makes me want to cry.
"We have got a a very fragile ecosystem in the park with the sticklebacks and Kingfishers."
Another resident, who wished to remain anonymous, said: "It's quite disgusting.
"I've seen the stream turn blue before - never seen anything like it."
When contacted by Bristol Live, the Environment Agency said the water had recently been tested by Wessex Water.
"They reported at the time the stream was running clear," the spokeswoman said.
"We have not have any reports of fish dying or any indication there's signification pollution."
The cause of the stream turning colour has yet to be established.
Wessex Water has been contacted for comment to determine when the tests were carried out.
A spokesman for Bristol City Council has said it is not something the council had been made aware of previously.
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