Aquapapa SB500 Bio Balls with Inside Sponge Design Filter Media for Aquarium Fish Pond Garden Waterfall Fountain, 500 Pcs Bio ball size: 1 inch in diameter. Bag size: 12"x 10.5". Bag dimensions with balls (Flat): 11x 9.5x 3. Approx.500 balls in 2 mesh bags. Ready-to-use media filter bags, convenient for use with your canister filter, power filter, or pond filter These bio balls are lightweight and typically float. They float so that the surface area can be close the air so that the bacteria get oxygen to thrive. With inside sponge design, it provides large surface area for cycle bacteria to colonize. Can be used in both fresh and saltwater aquarium and ponds.