Question

An aquarium owner, on a rather cold day, put a heater in his aquarium, which made the
water warm, but not hot. He thought the fish would like that. However, all his fish died.
What could be the reason for this?​

Answer 1

Answer:

fishes cannot live in hot water

Answer 2

As the water warms up the dissolved oxygen in it which the fish use for respiration becomes less. the solubility of oxygen decreases as temperature increases ¹. This means that warmer surface water requires less dissolved oxygen to reach 100% air saturation than does deeper, cooler water. ... Water at lower altitudes can hold more dissolved oxygen than water at higher altitudes.