Pea gravel
Also known as: Pea stone, River gravel, Aquarium gravel (smooth varieties)
Properties
| pH effect | varies by source |
|---|---|
| Water retention | very low |
| Drainage | excellent |
| Oxygen to roots | high |
| Bacterial surface area | moderate |
| Reusability | very high (essentially permanent) |
| Cost tier | low |
| Weight | very heavy |
How it affects the system
- pH depends entirely on stone composition: limestone-based gravel raises pH (vinegar test fizzes), silica/quartz/basalt gravel is inert
- Vinegar test BEFORE filling a system: drop white vinegar on a few stones; bubbling means calcium carbonate is present and the gravel will buffer pH upward
- Very heavy: a 4x8ft gravel media bed needs a solid stand and may need reinforced flooring
- Smooth surface compared to lava or clay pebbles: less bacterial colonization, biofilter capacity is moderate not high
System compatibility
Works well in:
- media bed (ebb and flow)
Avoid in:
- NFT channels
- deep water culture (rafts)
- drip
- wicking bed
Care notes
Cheapest viable media bed substrate in many regions. Always test for inertness before committing a system to it. Some commercial aquaponics farms use crushed basalt or river gravel exclusively for the cost advantage, accepting the lower biofilter performance.
Crops that work in pea gravel
1 edible crop in the catalog list this medium as compatible.
Sources
Data drawn from: aquaponics-association, community-experience. Last verified 2026-05-13.
Back to growing media reference