From the manufacturer's website:
What is a Aquatic Soil Perfector? Printer Friendly
Aquatic Soil Perfector is made from a naturally derived, ceramic granule that is kiln fired at temperatures in excess of 2000°F. This process created a durable granule containing thousands of tiny storages spaces that can hold oxygen and nutrients for plant roots to absorb. These granules are non-toxic, sterile and 100% inert. And unlike many potting soils containing peat moss, compost or other organic matter, Aquatic Soil Perfector’s granules will not float, decompose, or cloud the water in your pond when used as directed. Use Aquatic Soil Perfector for all potted aquatic plants such as water lilies, iris, lotus and others.
All Natural Soil Media for Potted Aquatic Plants
• Won’t float or cloud water.
• Anchors plants in pots.
• Non-toxic. Safe for all fish.
• Won’t clog pumps.
• Long lasting. Won’t degrade.
• Won’t affect pH.
• Holds oxygen and nutrients.
Directions
• Thoroughly rinse Aquatic Soil Perfector’s granules to remove any dust and ensure proper anchoring of plants.
• Line the bottom of your pot with 2 inches of Aquatic Soil Perfector.
• Set the plant in the pot and fill the pot with Aquatic Soil Perfector to about 1 inch below the rim of the pot.
• Top off the pot with decorative stones or gravel and sink pot slowly into water pond.