A small yellow robot developed by Chinese technicians is safeguarding coral reefs in the South China Sea.

When it finds crown-of-thorns starfish preying on coral polyps, the robot rushes and kills them.

The 45-cm-long, 29-cm wide and 22-cm-tall robot weighs less than 10 kilograms. Equipped with four high-power thrusters, it moves freely like a skilled diver.

The robot is an underwater observation device, designed and made by Qingdao Robotfish Marine Technology Co Ltd. Fan Ping is the company's chief technology officer.

Fan's team at first thought of calling it the Starfish-Killing Robot, but they eventually settled on Coral Guard.

Fan said the robot was tailor-made to protect coral polyps from the nibbling starfish and it also can fight off sea urchins.

"A coral reef is fragile and is one of the most complex ecosystems," Fan said recently, adding that protection of coral reefs can help save tens of hundreds of other species.

More important, protecting coral reefs is significant for maritime rights and interests, he emphasized.

Fan said his company's underwater robot is the third to prevent the threat to reefs from starfish, following those made by companies in Japan and Australia. Such robots are a welcome alternative to using chemicals and divers and they are safe and effective.

"Our robot monitoring range can reach 10 meters and it only allows 1 cm deviation from the target," he said, adding that is quite a feat for a small robot with present technology.

The robot began its testing stage in June and it was delivered to users in September.

"The miniaturization of robots is a trend of the future and has market potential in maritime preservation," Fan said. "It will be no surprise to see a group of small robots operating together underwater for marine observation in the future," Fan added.

Fan also said his company has just updated a new underwater robot that weighs less and has strong resistance against underwater currents with more advanced equipment such as a depth sensor and electronic compass. The new robot is expected to be used in aquaculture.

Fan is now designing a server and plans to establish a remote controller. After the new robot has undergone testing, people can operate the device and learn how it works by logging on to the company's website.