River gravel (pea gravel)
Also known as: Pea gravel, Smooth river rock, Drainage gravel
Workable
Properties
| Bacterial surface area | 50 m² per m³ |
|---|---|
| pH effect | neutral |
| Weight class | very heavy |
| Longevity | indefinite |
| Cost tier | low |
In a system
- Smooth, round, low-porosity stones at about 1500-1700 kg/m³ flooded; the heaviest common media by a wide margin
- Bacterial surface area is roughly a fifth of LECA, so beds need to be larger by area to handle equivalent fish loads
- Compacts in the bed over time; ebb-and-flow drainage stays even but daily probe inspection is needed in deeper beds
- Cheap and locally available almost everywhere; many builders use it to save money on the initial fill at the cost of a larger bed footprint
- Vinegar-test a sample before buying: if the gravel fizzes when wet vinegar is dropped on it, it's limestone gravel and will raise pH (see the entry on limestone)
Notes
Source from a landscape or aggregate supplier in 6-12 mm size. Avoid colored or coated gravel from pet stores; the coatings flake over years. Rinse thoroughly; landscape gravel often arrives dusty.
Sources
uvi-aquaponics-program, backyard-aquaponics-community
See the full aquaponics media reference for comparison, or use the aquaponics system designer to plan a complete setup.