Why do the fish in an aquarium die when temperature of is raised?

1. Increased metabolic rate: As water temperature increases, the metabolic rate of fish increases as well. This means that they need more oxygen to meet their energy demands. However, the solubility of oxygen in water decreases as temperature increases, so there is actually less oxygen available to the fish. This can lead to hypoxia, or oxygen deprivation, which can cause fish to die.

2. Stress: High temperatures can also be stressful for fish. This can lead to a weakened immune system, making fish more susceptible to diseases. Stress can also cause fish to produce more cortisol, a hormone that can damage tissues and organs.

3. Alterations in behavior: Elevated temperatures can also affect the behavior of fish, making them more aggressive and territorial. This can lead to injuries and further stress, exacerbating the other negative effects of high temperature.

4. Reduced feeding: Fish may stop or reduce feeding when water temperature becomes too high, leading to malnutrition and further health complications.

5. Disease: Certain fish diseases, such as ich and bacterial infections, thrive in warmer waters and can spread rapidly at elevated temperatures.

It's important to maintain a stable and appropriate water temperature in an aquarium to ensure the health and well-being of the fish. Most tropical fish are comfortable in a temperature range between 75-82°F (24-28°C). If the temperature fluctuates too much or exceeds safe levels, it can have serious consequences for the health and survival of the fish.