Question

A fish dies when it is put in an aquarium filled with previously boiled water but cooled to room temperature. This happens because the water in the aquarium is
1. depleted in oxygen
2. unfit for drinking by fish
3. depleted in minerals
4. unfit for swimming by fish

Answer 1

Correct Answer - Option 1 : depleted in oxygen

Concept:

• All living organisms need oxygen to live.
• Plants and animals directly take up oxygen from the air.
• Fish, like all other complex life forms, need oxygen to survive.
• They get theirs in the form of oxygen gas dissolved in the water.

​Explanation:

• Boiling creates bubbles that contain dissolved oxygen.
• When boiling the water the dissolved oxygen present in the water decreases.
• An increase in temperature results in decreased levels of dissolved oxygen in the water.
• This can harm aquatic animals such as fish, amphibians and other aquatic organisms.
• Cooling the water to room temperature speeds up the process of oxygen dissolution in the water.
• However, for higher dissolved oxygen level in the aquarium water more mixing and agitation are required.
• That's why it's important to have an aeration device, a bubbler, in the aquarium.

Thus, the fish dies when it is put in an aquarium filled with previously boiled water but cooled to room temperature because it is depleted of oxygen.