There are indeed lots of dead fishes along the banks of Sungei Tampines.
Media articles reported thousands of 5cm long dead fishes washed up along Sungei Tampines on 29 Mar, from Pasir Ris Drive 3 to the river mouth. I had a quick look this afternoon.
I started upstream where the Sungei is canalised, running under the busy Pasir Ris Drive 3.
I collected a few of the fishes so that the experts can have a closer look at them.
According to the media "In a joint statement yesterday evening, the PUB assured the public that yesterday's incident had no impact on drinking water quality. The NEA is also investigating the cause of the incident." There was a similar incident at Sungei Api Api on 20 Mar.
During this trip, I also saw hugging monitor lizards and other interesting wildlife.