Pumice
Also known as: Volcanic pumice, Horticultural pumice
Properties
| pH effect | neutral / inert |
|---|---|
| Water retention | low |
| Drainage | excellent |
| Oxygen to roots | high |
| Bacterial surface area | very high |
| Reusability | very high (essentially permanent) |
| Cost tier | moderate |
| Weight | light |
How it affects the system
- Lighter than lava rock with similar bacterial surface area: a good compromise medium for media beds where weight matters
- Less sharp than lava rock; safer for handling and on soft roots
- Regional availability: widely sold in volcanic regions (Pacific Northwest, Italy, Japan, New Zealand), harder to source elsewhere
- Mixed sizes available: smaller grades work for drip systems, larger for media beds
System compatibility
Works well in:
- media bed (ebb and flow)
- drip
- dutch bucket
Avoid in:
- NFT channels
- deep water culture (rafts)
Care notes
Underused medium that fills a niche between clay pebbles (expensive, manufactured) and lava rock (heavy, sharp). Where available locally, often cheaper than clay pebbles with better biofilter performance.
Sources
Data drawn from: cornell-cea, manufacturer-spec-sheets. Last verified 2026-05-13.
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