Key Features Highly porous, biological media for all types of aquarium filter. Plastic reusuable ball that contains a mini sponge foam. This foam creates more surface area for growth of beneficial bacteria Bio balls can be used in Aquarium and Pond filter systems to help to keep water clean and clear 50 Balls per Pack - 26mm Balls Pack of 1 - 50 Balls 50 Pack plastic BioBeads . Promotes oxygen gas exchange. Creates a large surface area for the ‘beneficial’ bacteria to colonise, increasing the break down of harmful Nitrates and Nitrites producing better quallity water for your fish. Highly porous, biological media for all types of aquarium filter. Average 50 balls per pack 26mm diameter Foam insert Free net bag for easy cleaning