# Clay pebbles

> Clay pebbles (LECA) are fired, expanded clay balls used as an inert hydroponic medium that drains freely, holds a little water and anchors roots.

- Canonical: https://genetixbay.com/knowledge/glossary/clay-pebbles.html
- Also written: LECA, expanded clay, clay balls, expanded clay aggregate, hydro pebbles
- Glossary category: Systems and media · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

Clay pebbles, or LECA (lightweight expanded clay aggregate), are small balls of clay fired in a kiln so they expand and become porous. They are pH-neutral once rinsed, hold almost no nutrients and only a little water inside their pores, and leave large air gaps between the balls. That makes them a classic support medium for hydroponic systems.

## In practice

Clay pebbles fill [net pots](https://genetixbay.com/knowledge/glossary/net-pot.md) in [DWC](https://genetixbay.com/knowledge/glossary/dwc.md) and [RDWC](https://genetixbay.com/knowledge/glossary/rdwc.md), fill trays in [ebb and flow](https://genetixbay.com/knowledge/glossary/ebb-and-flow.md), and line the base of containers. Rinse new pebbles well to remove dust that can clog pumps, and soak them before use. Because they dry quickly, plants grown purely in clay need frequent irrigation or roots that reach the solution. They can be washed, sterilised and reused for many cycles.

## Don't confuse with

- **Perlite**: much lighter and finer; usually mixed into a medium rather than used alone.
- **Pumice**: natural volcanic rock with a similar role; irregular shape.

## Related terms

[Net pot](https://genetixbay.com/knowledge/glossary/net-pot.md), [DWC](https://genetixbay.com/knowledge/glossary/dwc.md), [Ebb and flow](https://genetixbay.com/knowledge/glossary/ebb-and-flow.md), [Growing medium](https://genetixbay.com/knowledge/glossary/growing-medium.md), [Hydroponics](https://genetixbay.com/knowledge/glossary/hydroponics.md)

## Read more

- [Ebb and flow (flood and drain)](https://genetixbay.com/knowledge/systems/ebb-and-flow.md)
- [Deep water culture (DWC)](https://genetixbay.com/knowledge/systems/dwc.md)

## Sources

1. Resh HM, 2022. Hydroponic Food Production, 8th ed. CRC Press. https://doi.org/10.1201/9781003133254