Why do fish go crazy when you tap the tank?

Tapping on the tank creates vibrations and pressure waves that can startle or irritate fish. This is because their internal organs and fluid-filled bodies are highly sensitive to such disturbances in the water. Additionally, the unexpected changes in their environment may cause them to feel stressed and anxious. Some fish species may also perceive tapping on the tank as a threat or potential predator, leading to their erratic behaviour.