'Pollution incident' from drains at the Nook
It's now thought more than 140 fish died in what's being called a 'pollution incident' in Summerhill Glen, and the population 'could take several years to recover'.
Government's asking you to be extra careful what you put down your drains, after 143 fish were found dead there.
Officers believe the pollution came from 'the Nook', through surface water drains.
An officer from Manx Wildlife Trust made the discovery on Thursday, and staff from the Environmental Protection Unit and Fisheries Division took water samples for testing.
Nothing of concern was found in the water, which means whatever caused the problem is thought to have disappeared downstream by that time.
The dead fish included brown trout and sticklebacks, and it's thought there will also be a knock on effect on the other aquatic life that relied on them as a food source.