Expanded shale
Also known as: Haydite, Permatil, Expanded slate
Preferred
Properties
| Bacterial surface area | 200 m² per m³ |
|---|---|
| pH effect | neutral |
| Weight class | medium |
| Longevity | indefinite |
| Cost tier | moderate |
In a system
- Made by kilning shale at 1100°C until it puffs up; the result is a porous, hard, neutral-pH aggregate similar to LECA but denser
- Around 600-700 kg/m³ flooded, between LECA and lava rock for weight
- Irregular angular shape packs tighter than LECA, so a given bed holds slightly less water by void fraction
- Doesn't float, so beds can be filled and flooded immediately without a saturation step
- Commonly sold as a soil amendment in heavy clay regions (US Southeast); a 25 kg bag costs less than half what aquaponics-branded LECA costs
Notes
Rinse before use. The Permatil brand from Carolina Stalite is the most common North American source; comparable Spanish and Australian products go by 'expanded slate' or 'haydite'.
Sources
wilson-lennard-aquaponics-handbook, carolina-stalite-spec-sheet
See the full aquaponics media reference for comparison, or use the aquaponics system designer to plan a complete setup.