Biological filter media with bio-sponge. BIOBALL PLUS. Filter media for all aquarium filters. Suitable for both freshwater and marine aquariums. Its unique shape and structure with sponge filling provide the best environment for nitrifying bacteria, which help stabilize the pH level and keep the water clean and clear. BIOBALL PLUS also reduces the concentration of many toxic compounds, including heavy metal ions. It helps maintain optimal water quality. Before placing BIOBALL PLUS in the filter, rinse it with warm water.