A unique task for the taikonauts of Shenzhou-18 is to create an "aquarium" and raise fish in zero gravity.

They will create a simplified version of an aquatic ecosystem using zebrafish and algae to study how the space environment affects their growth and system balance. (Xinhua)

This photo taken on April 25, 2024 shows a backup version of the aquatic ecosystem. The three taikonauts aboard China's Shenzhou-18 spaceship have entered the country's space station and met with another taikonaut trio on Friday, starting a new round of in-orbit crew handover. (Xinhua/Jin Liwang)

This photo taken on April 25, 2024 shows a backup version of the aquatic ecosystem. The three taikonauts aboard China's Shenzhou-18 spaceship have entered the country's space station and met with another taikonaut trio on Friday, starting a new round of in-orbit crew handover. (Xinhua/Jin Liwang)

Researcher Wang Gaohong prepares the backup version of the aquatic ecosystem at Jiuquan Satellite Launch Center in northwest China, April 25, 2024. The three taikonauts aboard China's Shenzhou-18 spaceship have entered the country's space station and met with another taikonaut trio on Friday, starting a new round of in-orbit crew handover. (Xinhua/Jin Liwang)

A staff member observes the condition of the zebrafish for backup at Jiuquan Satellite Launch Center in northwest China, April 25, 2024. The three taikonauts aboard China's Shenzhou-18 spaceship have entered the country's space station and met with another taikonaut trio on Friday, starting a new round of in-orbit crew handover. (Xinhua/Jin Liwang)

Staff members transfer the integrated aquatic ecosystem sample for the Shenzhou-18 spaceflight mission at Jiuquan Satellite Launch Center in northwest China, April 25, 2024. The three taikonauts aboard China's Shenzhou-18 spaceship have entered the country's space station and met with another taikonaut trio on Friday, starting a new round of in-orbit crew handover. (Xinhua/Jin Liwang)

Staff members pose for a group photo with the integrated aquatic ecosystem sample for the Shenzhou-18 spaceflight mission at Jiuquan Satellite Launch Center in northwest China, April 25, 2024. The three taikonauts aboard China's Shenzhou-18 spaceship have entered the country's space station and met with another taikonaut trio on Friday, starting a new round of in-orbit crew handover. (Xinhua/Jin Liwang)

A staff member processes the algae at Jiuquan Satellite Launch Center in northwest China, April 25, 2024. The three taikonauts aboard China's Shenzhou-18 spaceship have entered the country's space station and met with another taikonaut trio on Friday, starting a new round of in-orbit crew handover.(Xinhua/Jin Liwang)

A staff member observes the condition of the zebrafish for backup at Jiuquan Satellite Launch Center in northwest China, April 25, 2024. The three taikonauts aboard China's Shenzhou-18 spaceship have entered the country's space station and met with another taikonaut trio on Friday, starting a new round of in-orbit crew handover. (Xinhua/Jin Liwang)