Round Clay Balls are lightweight and used to decorate an aquarium. It is also a good potting medium and the best option for top dressing.
So you're choosing a hydroponic or aquaponic media, and hydroton (clay pebbles) is on your list.
Good! Hydroton is worth considering.
What is Hydroton?
As the balls heat up, they fill with bubbles and form into small marble-sized units. While the clay can be used on its own for growing plants, it can also be mixed with soil and other growing media. Hydroton is used widely in hydroponics and aquaponics.
Expanded clay aggregates are formed by heating natural clay at 1200 degrees Celsius temperature. This results in developing a honeycombed structure interconnected within a clay ball. The clay balls are generally round in shape. These are extremely lightweight and strong. Clay balls do not change the pH of the soil.
Clay pebbles are lightweighted and it's porous holds air in them and increases the aeration for the root system of the plant. The structural formation of these hydrotons is such that it is light in weight and has enough space inside to capture the air and let it release whenever the plants or harvest needs it.
It is not the source of nutrients but can hold on nutrients, moisture and increase aeration in soil.