What is toxic in an aquarium?

Toxic substances in an aquarium primarily include ammonia, nitrites, and nitrates, which can accumulate from fish waste, uneaten food, and decaying plants. High levels of ammonia and nitrites are particularly harmful, causing stress or death to fish and other aquatic life. Additionally, certain chemicals like chlorine, chloramine, and heavy metals can also be toxic, affecting water quality and the health of the aquarium inhabitants. Regular water testing and maintenance are essential to prevent toxicity and ensure a healthy aquatic environment.