Sulphur Upwelling Causes Mass Death of Red Devil Fish at Lake Batur
Carcasses of the red devil fish (Amphilophus labiatus) have been scattered along the edge of Lake Batur in Kintamani District, Bangli. The fish died en masse as a result of a sulphur eruption.
An observation by detikBali found hundreds of dead red devil fish floating beneath a platform on the western side of Kedisan Village pier. A fishy stench could be detected from two metres away.
Several red devil carcasses were also visible several metres to the west of the lake’s banks. The physical condition of the dead predator fish had already turned white, suggesting they had died several days earlier.
Meanwhile, sulphur patches were also visible on the lake from a distance. The water of Lake Batur appeared to have turned bright green or pale as a result of the sulphur eruption.
“Mostly it’s the red devil fish that died. Those are wild fish, not tilapia,” said one floating-net-cage fish farmer, who declined to give his name, when met by detikBali at Kedisan Village pier on Thursday (23/7/2026).
The farmer said many tilapia in the cages had also been affected by the sulphur spill. Hundreds of fish in the cages could be seen gasping for oxygen by poking their snouts above the water’s surface. As a result, all the farmers chose not to approach their cages, leaving the tilapia to try to find oxygen on their own.
“Because when the water is hit by sulphur, there’s no oxygen left. So the fish breathe by seeking oxygen at the surface. During that time, no farmer dared to check their cages,” he said.
The farmer said some had harvested their farmed tilapia early to prevent losses. Other residents were catching surviving red devil fish to be sent to Negara District in Jembrana.
Red devil fish are farmed by residents in Jembrana to be processed into fishmeal. The fish, considered a pest, is priced at Rp 2,000 per kilogram.
“But the fish are not poisonous. The sulphur content in the lake water only causes oxygen depletion. So the fish can’t breathe. But it’s not toxic,” he explained.
As previously reported, the sulphur spill at Lake Batur began several days ago. The sulphur first overflowed along the lake banks in Buahan Village and Abang Dukuh Village.
The sulphur flow drifted with the lake current, pushed by the wind towards the west. The police confirmed they had been conducting patrols since the sulphur content surged from the lake bed.
Since then, fish farmers have been urged not to release new tilapia fry to prevent losses. In addition, farmers have also been advised to bury tilapia killed by the sulphur rather than dumping the carcasses into the lake.