Question

We generally do not clean ponds or lakes but the aquarium needed to be cleaned frequently why

Answer 1

Answer:

Cleaning up a pond or a river is too expensive for anyone and it is the duty of the government but cleaning up of aquarium is all about personal hygiene since no vectors like mosquito can breed in it and even from animal point of view the concentration of pathogens is negligible when compared to the small aquarium.

Answer 2

A pond is a natural ecosystem where animals found in all trophic level are present.Therefore in ponds decomposers are also present.They decompose the dead material.
Whereas Aquarium is artificial ecosystem.Here decomposers are not found.Therefore we have to clean it manually.