Jakarta. Authorities in South Jakarta are aiming to remove up to 10 tons of invasive “janitor fish” from local waterways, stepping up efforts to protect native species, address public health concerns, and restore ecological balance.

South Jakarta Mayor Muhammad Anwar said the operation is being carried out alongside strict disposal procedures that follow recommendations from the Indonesian Ulema Council (MUI), to avoid public misunderstanding.

“To prevent any confusion going forward, we are carrying out this process in accordance with MUI’s advice. Today’s operation has gone well,” Anwar said on Tuesday.

Joint teams conducted the latest sweep near Setu Babakan, targeting around 5 tons of the fish. The effort follows a similar operation last week that removed approximately 5.3 tons, bringing the total close to the 10-ton target.

Authorities said all fish collected during the operation were already dead before being buried, addressing concerns over proper handling.

Read More: Jakarta Begins Mass Removal of Invasive ‘Janitor Fish'

MUI Calls for Ethical Handling of Fish Removal
The operation comes after scrutiny from the MUI’s Fatwa Commission over earlier reports that some fish may have been buried alive. KH Miftahul Huda, secretary of the commission, warned that such practices would violate principles of compassion and animal welfare.

However, he acknowledged that efforts to control the invasive species carry clear public benefit, describing them as part of environmental protection, given the fish’s destructive impact on river ecosystems.

The janitor fish, also known as pleco, thrives in polluted waters and preys on the eggs of native species, contributing to declining fish populations. “Local fish populations are decreasing because their eggs are being eaten by janitor fish,” Anwar said.

Food Safety Concerns Emerge
Beyond ecological concerns, the fish has recently drawn public attention for another reason: its suspected use in low-cost street food. Discussions have intensified following reports of rising janitor fish populations in the Ciliwung River, where some individuals have been seen catching the fish to process into foods such as siomai (Indonesian-style dumplings).

Authentic siomai made from mackerel typically sells for between Rp 3,000 and Rp 7,000 per piece, depending on size and location. By contrast, unusually cheap siomai priced at Rp 1,000 to Rp 2,000 per piece has raised suspicion among consumers.

Health experts warn that the primary risk lies not in the fish itself, but in its habitat. Siti Nadia Tarmizi, director of non-communicable diseases at the Health Ministry, said janitor fish are not inherently toxic.

“We need to distinguish between the species and its environment. Fish living in polluted waters are more likely to contain harmful substances, not because the fish itself is poisonous,” she said.

Janitor fish are commonly found in contaminated rivers and urban waterways, increasing the risk of exposure to heavy metals such as mercury, lead, cadmium and arsenic. Studies show these substances can accumulate in fish tissue over time through a process known as bioaccumulation.

Long-term consumption of contaminated fish has been linked to serious health risks, including neurological disorders, kidney damage and potential cancer.

Intensified Capture Efforts to Contain Spread
To curb the spread of the species, authorities plan to intensify capture operations twice a week, focusing on upstream areas to prevent further downstream migration. Officials also expect the program to improve water quality over time.

The operation involves around 60 personnel from the South Jakarta administration, the Indonesian military and local communities.

Residents have welcomed the initiative. Yanuar Hadi, 47, said controlling the invasive species is crucial to preserving local fish stocks and protecting public health.

“We support this effort because controlling janitor fish is better than losing our local fish,” he said.

City officials hope sustained intervention will restore ecological balance in Jakarta’s waterways while reducing risks tied to pollution and unsafe consumption.