What happens if you leave a dead fish in the tank and how does it affect the aquarium ecosystem?

Leaving a dead fish in the tank can lead to an increase in ammonia levels as the fish decomposes, which can harm other fish and plants in the aquarium. This can disrupt the balance of the ecosystem, potentially leading to illness or death of other aquatic life. It is important to promptly remove any dead fish from the tank to maintain a healthy aquarium environment.