Why we clean an aquarium but not a pond or lake

The same question, asked 3 times: 2022*, 2023*, 2025. Every wording below, oldest first.

Try each one first, then open its answer.

Question 1
2022
7 (b) $(i) List two human-made ecosystems. (ii) “We do not clean a pond in the same manner as we do in an aquarium.” Give reason to justify this statement.$
Question 2
2022
13 $(a) We do not clean ponds or lakes, but an aquarium needs to be cleaned regularly. Why ? (b) Why is ozone layer getting depleted at the higher levels of the atmosphere ? Mention one harmful effect caused by its depletion.$
Question 3
2023
26 $We do not clean ponds or lakes but an aquarium needs to be cleaned regularly. Why ?$
Question 4
2025
26 $We do not clean natural ponds or lakes whereas an aquarium or a swimming pool needs to be cleaned regularly. Why ?$

Question 1