Aquarium fish are danger to rivers - 18th May 2026

Indonesia's government is trying to stop the sapu-sapu. The tropical fish is originally from South America. But now, it's living in the country's rivers.

Sapu-sapu are often used to clean home aquariums. That's how the fish, which is also called the suckermouth catfish, arrived in Indonesia. But they can grow to a length of 50 centimetres.

At this size, they're too large for many fish tanks. So, people placed them in local rivers. But each year, female sapu-sapu lay thousands of eggs. As a result, they've gradually taken over.

Sapu-sapu have taken all the food from local fish. They also don't require much oxygen, which has given them another advantage. This is because many Indonesian rivers are highly polluted.

The situation's extremely difficult in the capital city, Jakarta. Now, local residents are working with soldiers and other government employees.

Their plan is to catch all the sapu-sapu in the city's rivers. In South Jakarta, 5.3 tonnes of sapu-sapu were caught in just two weeks.

Large nets are used to catch the fish. Any local fish are put back in the river. The sapu-sapu are then killed and buried. They can't be eaten because they're full of toxins, explains Mayor Muhammad Anwar.

Muhammad Anwar: "It contains heavy metals and is dangerous to humans."

When animals are transported to different regions, they frequently damage the local environment. The UN estimates that the global cost of this damage is $400 billion a year.