Natural water bodies are not regularly cleaned whereas an aquarium needs regular cleaning . Why
Answers
Natural water bodies like ponds and lakes not need to clean regularly because in ponds and lakes decomposing organisms are present to breakdown the waste materials into small particles, but in aquarium these decomposing organisms are not present so we need to clean regularly the aquariu .
Natural water bodies which hold aquatic life are usually large, has plant growth in them and is fed by natural water flow. All this provides fresh oxygen and food materials which are essential for aquatic life.
An aquarium is an enclosed artificial space which holds water and aquatic life in it. The scope for rejuvenation of oxygen in this restricted space is very little and hence it has to be cleaned regularly and the water replaced with fresh or salt water, depending on the type of aquatic life in it.