Bundaberg Regional Council staff are investigating the death of fish at the Botanic Gardens.
A council spokesman said hot and dry conditions are believed to have contributed to the incident. A similar event occurred in January last year.
“The fish kill is most likely a result of inadequate oxygen levels and high algae levels in the upstream lake,” the spokesman said.
“There have been very hot still conditions and water quality is poor due to low rainfall, no inflows and birds roosting, causing high nutrients and algae blooms.”
It's hoped that forecast rain this weekend will improve inflows and water quality.