Provides maximum surface area with the greatest possible mix of air and water. Cultivates nitrifying bacteria. Promotes gas exchange, increases dissolved oxygen level and removes harmful gases. Will not clog with organic matter. Manufactured of the highest grade thermoplastic material. Totally inert and nonleaching. Use in any type of Aquarium or Pond Filter to increase performance. FOAM FILLED = Clean, Aerate, Biological 1 1/2 Carbon Filled = Purify, Aerate, Biological 1 1/2 Ceramic Filled = Aerate, Biological 1 1/2 Standard Solid = Aerate, Biological 1 and 1 1/2.