How much gravel for a 90 gallon tank?
48 × 18 × 24 in · freshwater planning
90 gallon · gravel & substrate
The working
48 × 18 × 2 = 1,728 in³. Divide by 1,728 and multiply by 100 lb/ft³ = 100 lb. Round up to 5 bags of 20 lb.
| Depth | Gravel lb / 20 lb bags | Sand lb / 20 lb bags | Aquasoil lb / L |
|---|---|---|---|
| 1 in | 50 / 3 | 50 / 3 | 30 / 14.16 |
| 2 in | 100 / 5 | 100 / 5 | 60 / 28.32 |
| 3 in | 150 / 8 | 150 / 8 | 90 / 42.48 |
90 gallon equipment and layout plan
A low, extended rectangle puts more of the layout along a horizontal swimming lane. The 48 × 18-inch base has an aspect ratio of 2.67:1. A lid or light must span roughly 48 inches; measure rim openings and bracket adjustment before ordering.
| Level bed | Sand bags, rounded up | Aquasoil bags, rounded up |
|---|---|---|
| 1 in | 50 lb / 3 × 20 lb | 14.16 L / 2 × 9 L |
| 2 in | 100 lb / 5 × 20 lb | 28.32 L / 4 × 9 L |
| 3 in | 150 lb / 8 × 20 lb | 42.48 L / 5 × 9 L |
For this large base, budget 28.32 L for a continuous 1-to-3-inch front-to-back slope. The shallow edge runs 48 inches, with the rise extending over 18 inches. Hardscape or terraces change the covered area. Buy soil by litres; estimated bulk density does not establish how much a particular package weighs.
Compared with the 75 gallon, this layout has the same 864 square inches of substrate coverage. Extra nominal capacity alone does not change this requirement.
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 1.11 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
First decisions for this large setup
For this 48-inch run, distribute unopened bags along the work area before filling. Calculate planted zones separately if only part of the base needs deep soil. A shallow open sand lane and deeper rear planting area require an area-weighted average; the full-footprint table deliberately assumes uniform coverage.
How to use this plan
- Measure the inside footprint; this plan uses 48 by 18 inches.
- Choose an average depth, allowing for slopes and hardscape.
- Calculate volume and mass as above; buy about 5 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 90 gallon calculation use?
It uses a rounded 48 × 18 × 24 inch rectangle. Actual dimensions vary by brand and frame; measure your own tank.
What is the gravel & substrate estimate for a 90 gallon tank?
100 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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