Construction of a stable and efficient multi-nutrient-level landscape ecosystem is a hotspot of the aquarium industry these years. In order to explore the changes in the structure and stability of the microcosmic ecosystem after the introduction of macroalgae in aquariums, water quality indicators, bacteria and plankton community structure analysis were carried out in different treatment groups. The results showed that: The rising trend of DO and pH in the algae group was higher than those of the non-algae group, and the content of NO₂^--N could be kept at a low level. The content of PO₄^3--P and NH₄⁺-N was significantly lower than those of the non-algae group (P<0.05). The bacterial diversity and evenness index of the algae-group were significantly lower than those of the non-algae group (P<0.05); the plankton community evenness index was highly different among three groups (P<0.05). Bacterial community structure analysis results showed that the first and second dominant bacteria phyla of the non-algae groups and algae-groups were Proteobacteria and Actinobacteria. The abiotic control-groups were Proteobacteria and Firmicutes. The first dominant phylum of plankton communities in each treatment group was Bacillariophyta, accounting for at least 40% of the abundance of plankton communities in the sample. The first dominant genus is Melosira. CCA results showed that the abundance of dominant species in the non-algae group had a positive correlation with the nutrient content and was negatively associated with DO and pH while the algae-group was the opposite. The results indicate that the microcosmic system plankton and bacterial community composition of different nutritional levels are different. Cultivating Caulerpa sertularioides can effectively improve water quality of the ecological aquarium and affect the microcosmic structure, which helps to bulid a stable and efficient landscape ecosystem.