Operationally, the algae water can be kept fresh by simply replacing some of the algae water every week and diluting it to remove the aging algae. Functionally, the product can effectively solve the problem of excessive indoor CO2, and it has the function of a normal air purifier and can also produce O2. With the mechanism of the machine the air is refined and absorbed into alkaline algae water; in the meantime, the air is cleaned with algae water.