Perlite can be used to regulate the water in your garden. Since it is a volcanic rock with a high water content, if you mix it in with your garden soils, it prevents water from being absorbed by your soil. This makes it good to amend clay soil with. Also, it allows for good aeration of the soil. This is because the pellets loosen up the soil, which allows air to permeate deep down better than soil without perlite. This allows oxygen in limited quantities to get to the roots, which aids soil ratios, plant growth, and vitality.