Aquarium additives are substances added to fish tanks to improve water quality and support the health of aquatic life. These products can include water conditioners, which remove harmful chemicals like chlorine, and beneficial bacteria that help break down waste. Other common additives are fertilizers for aquatic plants and medications for treating fish diseases. Using the right additives can create a balanced environment, ensuring that both fish and plants thrive in their aquarium ecosystem. Regular testing of water parameters is essential to determine which additives may be needed.