You might have seen an aquarium. Let us try to design one.
What are the things that we need to keep in mind when we create an aquarium? The fish would need a free space for swimming (it could be a large jar), water, oxygen and food.
We can provide oxygen through an oxygen pump (aerator) and fish food which is available in the market.
If we add a few aquatic plants and animals it can become a selfsustaining system. Can you think how this happens? An aquarium is an example of a human-made ecosystem.
Can we leave the aquarium as such after we set it up? Why does it have to be cleaned once in a while? Do we have to clean ponds or lakes in the same manner? Why or why not?
✅ Answer: We cannot leave the aquarium as such after we set it up. Decomposed food particles, dead plant parts, excreta of the fishes etc. accumulate in the water. Thus concentration of nitrogenous waste and microorganisms increase. So, aquarium needs to be cleaned regularly.
A pond or lakes need not to be cleaned in this manner because they are large sized ecosystems. They contain much water. Also they get new water by the phenomenon such as rain.