Invasive “Janitor Fish” Take over Jakarta’s polluted rivers

Added: 2026-05-16

[00:00:00]So, this is the common pleco, also  known as the sucker mouth catfish, an invasive species from South America that's  now thriving in the polluted rivers of Jakarta.

[00:00:13]One study from last year suggests some areas of  the city have infestations of up to 100%. I'm on the Chileong River and I've come here to meet  Arif, a content creator on a mission to reduce the population of these fish. I might catch around  30 to 40 fish per day. My personal record was catching 70 kgs in one outing. I usually use  nets and sometimes I use my hands to take the eggs. Experts say the catfish came to Indonesia  through the ornamental fish trade. It earned the nickname janitor fish for its ability to clean  algae off the glass in aquariums. But they've taken over many rivers and lakes. The Chileong  River is heavily polluted with domestic and industrial waste and that's resulted in severe  biodiversity loss with many freshwater species unable to survive in these conditions. And yet in  these same waters, the population of the common plecco is growing. They're bottom feeders and  will eat almost anything. Instead of scales, the fish are covered in thick armor-like plates  and have few natural predators. As a result, the Jakarta government is undertaking a  city-wide effort to remove the species from the capital's waterways. These men have spent  the morning culling thousands of common plecco, but experts say it's a difficult task. The  fish are highly resilient. A female plecco can lay thousands of eggs per cycle, and so reducing  their population will require a long-term effort.

[00:01:54]The catfish lays eggs in deep burrows in river  banks and riverbeds, which worsens erosion. These burrows keep eggs protected, meaning most hatch  successfully. Even if we catch them every week, it's difficult to reduce their numbers, let  alone eliminate them. These fish will be cold and buried. They aren't safe for consumption because  of their exposure to pollution. Marine experts say this is just one step towards restoring  the ecosystem and that the more important task is to improve water quality by reducing  pollution. Jessica Washington, Alazer, Jakarta.