Answer:
ecosystem
Step-by-step explanation:
An ecosystem is the biological community of organisms that interact with each other and they share the same physical environment. Even though it is man-made, the aquarium still represents an ecosystem. The aquarium itself is the physical environment in which all the organisms in it live. Since all the fishes live together, they interact with each other in one way or another, thus creating an interactive biological community, resulting in a micro ecosystem.