Aquaponics grow-bed media
What goes inside a media bed. Aquaponics chooses substrate primarily for bacterial surface area (the bed is the biofilter), with weight, longevity, and pH effect as secondary criteria. Different decision space from hydroponic media (which prioritizes water retention and root contact) and from aquarium substrate (which is about plant rooting and water chemistry).
9 substrate profiles, grouped by recommended use. The aquaponics system designer lets you pick bed types; this page tells you what to fill them with.
Preferred
These media are what most aquaponics setups use. Good biofilter surface area, manageable weight, long lifespan.
| Medium | Bacterial surface | pH effect | Weight | Longevity | Cost |
|---|---|---|---|---|---|
| Expanded shale | 200 m²/m³ | neutral | medium | indefinite | moderate |
| Lava rock (scoria) | 400 m²/m³ | alkaline at first (washes off) | medium | indefinite | low |
| LECA (clay pebbles) | 250 m²/m³ | neutral | very light | 10 years | moderate |
Workable
These will work but trade something off (more weight, less surface area, larger bed needed for the same fish load).
| Medium | Bacterial surface | pH effect | Weight | Longevity | Cost |
|---|---|---|---|---|---|
| River gravel (pea gravel) | 50 m²/m³ | neutral | very heavy | indefinite | low |
Situational
These solve specific design needs (raft beds, wicking beds, supplemental biofilters) but aren’t standalone media-bed substrates.
| Medium | Bacterial surface | pH effect | Weight | Longevity | Cost |
|---|---|---|---|---|---|
| Bio-balls (plastic biofilter media) | 500 m²/m³ | neutral | very light | indefinite | moderate |
| Net cups (raft / DWC beds) | n/a | neutral | very light | 10 years | low |
| Wicking bed soil mix | n/a | slightly acidic | medium | 3 years | moderate |
Avoid
These actively harm aquaponics systems. Documented here so you recognize them by other names if someone suggests them.
| Medium | Bacterial surface | pH effect | Weight | Longevity | Cost |
|---|---|---|---|---|---|
| Aquasoil (aquarium plant substrate) | 300 m²/m³ | slightly acidic | medium | 3 years | high |
| Limestone gravel | 80 m²/m³ | raises pH permanently | very heavy | indefinite | low |