Aquarium substrate calculator
How much gravel or sand does your tank actually need? Enter the footprint and how deep you want the bed, and get the amount to buy in pounds, kilograms and litres.
Aim for about 1 inch for a fish-only tank and 2 to 3 inches if you are rooting plants. Sand packs tighter, so keep it shallower. Aqua soil is usually sold by the litre, so use the litre figure for that.
How it is worked out
The bed is just a box of material: length × width × depth gives its volume, and multiplying by the material's density gives the weight. Aquarium gravel runs about 100 pounds per cubic foot and sand a little more; aqua soil is lighter and is usually sold by the litre, so use the litre figure for that.
How deep should the substrate be?
About 1 inch is plenty for a fish-only tank you just want to look planted. For rooted plants, go 2 to 3 inches so roots have somewhere to anchor and feed. Sand packs tighter than gravel, so keep sand beds on the shallow side to avoid dead spots.
Buy a little extra
Substrate settles and you always lose a little to rinsing, so round up when you buy. If you are keeping plants, size the rest of the setup with the volume calculator and feed roots with the picks in our root tabs and fertiliser rankings.
Source
- Volume = length × width × depth; density approximations: gravel ≈ 100 lb/ft³, sand ≈ 105 lb/ft³, aqua soil ≈ 55 lb/ft³ (standard reference ranges; grain size varies).
Common questions
How much gravel do I need for a 20-gallon tank?
A standard 20-gallon (about a 24 x 12 inch footprint) needs roughly 20 pounds of gravel for a 1-inch bed, or around 40 pounds for a planted 2-inch bed. Enter your exact footprint and depth for the precise amount.
How deep should aquarium substrate be?
About 1 inch for a fish-only tank, and 2 to 3 inches if you are rooting plants so roots can anchor and feed. Keep sand shallower, since it packs tighter than gravel.
How much sand for a 40-gallon tank?
Sand is a little denser than gravel, so a 40-gallon breeder (about a 36 x 18 inch footprint) needs roughly 55 to 60 pounds for a 1-inch layer. Use the calculator with your footprint and desired depth.
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