LECA (clay pebbles)
Also known as: Hydroton, Expanded clay, Light expanded clay aggregate, Clay pebbles, Grow rocks
Preferred
Properties
| Bacterial surface area | 250 m² per m³ |
|---|---|
| pH effect | neutral |
| Weight class | very light |
| Longevity | 10 years before degradation |
| Cost tier | moderate |
In a system
- Lightest of the common biofilter media at roughly 300 kg/m3 flooded, so bed structure (timber, IBC tote, fibreglass) need not be heavily reinforced
- Round pebbles with rough internal porosity give around 250 m2/m3 of bacterial surface area, enough for typical hobby fish loads
- Floats when dry, so beds must be flooded slowly the first time or weighted; once saturated it stays put
- Reusable indefinitely with a hot-water rinse between cycles, with no measurable degradation over 10+ years of continuous use
- Drains and re-floods cleanly in ebb-and-flow beds because the round, uniform 8-16 mm pebbles do not pack tightly
Notes
Rinse new pebbles thoroughly before use, or the manufacturing dust clouds the water for days. Cheaper hydroponics-grade brands work as well as premium ones, since the manufacturing process is the same: clay fired in a rotary kiln at around 1,200 C until it expands into light, porous, near-neutral aggregate.
See the full aquaponics media reference for comparison, or use the aquaponics system designer to plan a complete setup.