Feng Shui Decorative Pebbles - Polished Jade - 3 Pack Recommended Quantites per Biorb: The quantity needed to completely cover the bottom of your biorb will vary depending on the size, below is our recommendation for each. Baby Biorb 4 Gallon: 2 packs/4 lbs. Biorb 8 Gallon: 3 packs/6 lbs. Biube 9 Gallon: 3 packs/6 lbs. Biorb Life 45: 4 packs/8 lbs. Biorb 16 Gallon: 5 packs/10 lbs.