We do not clean ponds or lakes, but an aquarium needs to be cleaned. Why ?

We do not clean ponds or lakes but an aquarium needs to be cleaned periodically. Why ?

(a) Natural water bodies are not regularly cleaned whereas an aquarium needs regular cleaning. Why ? (b) What are decomposers? What will be the consequence if the decomposers are completely eradicated from an ecosystem? Give justification in support of your answer.

Why does aquarium have to be cleaned once in a while?

Why do you need to clean an aquarium periodically while ponds do not need to be cleaned?

Alkanes generally burn with a clean flame . Why?