Clay pebbles can be a very economical choice for the home gardener. They do not work particularly well in large pots because of their poor nutrient-lifting ability, but they are very effective in smaller pots and containers. You can also rinse and re-use the pebbles indefinitely, which reduces the upkeep cost of your indoor garden. Clay pebbles by themselves are pH neutral and do not retain any nutrients. Their round shape creates natural airholes throughout the pot, which ventilates the roots and prevents rotting.
Clay pebbles are usually used in conjunction with net pots in flood and drain hydroponic systems. The pebbles work well in these systems because they allow free flow of the water through the plant's roots, which is key for circulating nutrients. If you are using a drip irrigation hydroponic system, mix the pebbles with a more absorbent medium to provide better nutrient transportation and retention.