How much gravel for a 29 gallon tank?
30 × 12 × 18 in · freshwater planning
29 gallon · gravel & substrate
29 gallon equipment and layout plan
A rectangular layout supports a straight front swimming lane and a rear equipment zone. The 30 × 12-inch base has an aspect ratio of 2.5:1. A lid or light must span roughly 30 inches; measure rim openings and bracket adjustment before ordering.
| Level bed | Sand bags, rounded up | Aquasoil bags, rounded up |
|---|---|---|
| 1 in | 20.83 lb / 2 × 20 lb | 5.9 L / 1 × 9 L |
| 2 in | 41.67 lb / 3 × 20 lb | 11.8 L / 2 × 9 L |
| 3 in | 62.5 lb / 4 × 20 lb | 17.7 L / 2 × 9 L |
To build a slope along the 30-inch front, calculate a shallow 1-inch strip and a deep 3-inch rear bank. Their average depth is 2 inches if the slope is linear across 12 inches. Buy 11.8 L before accounting for rocks. Soil counts assume 9 L packages, not a guaranteed bag weight.
Moving up from the 25 gallon changes square inches of substrate coverage from 288 to 360: an increase of 25%. Budget for the larger requirement rather than reusing the smaller plan unchanged.
First decisions for this small setup
Lay out the 30-inch front edge before pouring substrate. Keep a clear strip where the siphon will reach, and place heavy hardscape securely rather than relying on loose gravel to hold it upright. Rounded-up bag totals leave surplus: do not pour every bag in just because it was purchased.
The working
30 × 12 × 2 = 720 in³. Divide by 1,728 and multiply by 100 lb/ft³ = 41.67 lb. Round up to 3 bags of 20 lb.
| Depth | Gravel lb / 20 lb bags | Sand lb / 20 lb bags | Aquasoil lb / L |
|---|---|---|---|
| 1 in | 20.83 / 2 | 20.83 / 2 | 12.5 / 5.9 |
| 2 in | 41.67 / 3 | 41.67 / 3 | 25 / 11.8 |
| 3 in | 62.5 / 4 | 62.5 / 4 | 37.5 / 17.7 |
Assumptions and limits
The old 1 lb/gal for roughly 1 inch and 1.5–2 lb/gal for 2 inches rules are loose shopping shortcuts. Here a 2-inch bed is 1.44 lb per nominal gallon. Footprint and bulk density explain the difference. Gravel and sand use 100 lb/ft³; aquasoil uses 60. Check bag coverage; grain size and moisture change density.
Bulk densities are stated planning assumptions; litre conversion: NIST conversion tables
How to use this plan
- Measure the inside footprint; this plan uses 30 by 12 inches.
- Choose an average depth, allowing for slopes and hardscape.
- Calculate volume and mass as above; buy about 3 20 lb bags for a level 2-inch gravel bed.
Adjust measurements with the gravel & substrate calculator
Questions before you buy
What dimensions does this 29 gallon calculation use?
It uses a rounded 30 × 12 × 18 inch rectangle. Actual dimensions vary by brand and frame; measure your own tank.
What is the gravel & substrate estimate for a 29 gallon tank?
41.67 lb gravel for a 2-inch bed
Equipment to check
Compare aquarium substrate. Check dimensions, capacity and product instructions before buying.
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