These plants not only serve as decoration, but more importantly, they play a role in air circulation. The pure water used by the crew goes through a circulation system to feed the plants. After a second cycle, it can be used for sanitation supply, and then multiple water purifiers made by Lin Xian filter out waste, recirculating the water back for drinking.
Although it sounds somewhat disgusting, in the post-apocalyptic world, there's no other choice. Clean water without dark invasion is extremely scarce. In fact, according to the filtration standards of the A1-level subcritical reverse osmosis water purifier made by Lin Xian, combined with the Heterogeneous Rubik's Cube's shielding of dark invasion power, the water drunk by the Infinity members has always been at Level 1 pure water standard, so the number of cycles doesn't affect much.
