(240426) -- JIUQUAN, April 26, 2024 (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. 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/Jin Liwang)