Substrate depth guide

Aquarium Substrate Calculator

Estimate substrate volume, weight, and bag count for planted, reef, and freshwater tanks.

Download the checklist

Keep the practical checks, caution notes, and next steps handy while comparing options.

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Common use cases

Planted tank depth Plan depth around root growth, layout shape, and the substrate type you intend to use. Substrate density The same volume can weigh differently depending on whether you use sand, gravel, or aqua soil. Tank size examples Use common footprints to sanity-check your calculator result before buying bags. Sand vs gravel The same tank footprint and depth can need different bag counts depending on substrate density. Sloped aquascapes Use an average depth for the calculator, then add allowance for steep slopes and hardscape.

Worked examples

Pre-calculated results for common situations. See all examples.

60 x 30 cm tank A starting estimate for a 60 x 30 cm tank at 5 cm substrate depth. 90 x 45 cm tank A starting estimate for a 90 x 45 cm tank at 5 cm substrate depth. 120 x 50 cm tank A starting estimate for a 120 x 50 cm tank at 6 cm substrate depth. 45 x 30 cm nano tank A starting estimate for a 45 x 30 cm nano tank at 4 cm substrate depth. Planted 90 x 45 cm tank A starting estimate for a planted 90 x 45 cm tank at 8 cm substrate depth.

How this estimate works

The calculator turns tank footprint and desired depth into volume, converts that volume to weight using substrate density, then rounds bag count up.

Volume in litres = length x width x depth in cm divided by 1000.
Weight = volume x substrate density x a 10% setup allowance.
Bag count is always rounded up to avoid running short during layout.

Before buying substrate

Check the needs of your livestock and plants, then confirm bag weights and substrate density from the brand you plan to use.

Worked example

A 90 x 45 cm tank with 5 cm of substrate needs about 20.3 litres. At 1.4 kg/L with a small allowance, that is about 31.2 kg, so four 9 kg bags.

Substrate depth examples

Depth depends on layout, livestock, plants, and the substrate type. These examples are planning ranges, not species guidance.

Tank footprint	Depth	Approximate volume
60 x 30 cm	3 cm	5.4 litres
60 x 30 cm	5 cm	9 litres
90 x 45 cm	5 cm	20.3 litres
120 x 45 cm	6 cm	32.4 litres

Before you add substrate

Decide whether the layout is flat, sloped, or planted before estimating depth.
Check whether the substrate should be rinsed before use.
Confirm the bag weight and density for the exact brand.
Leave enough free space for hardscape, filters, and livestock needs.

When this estimate may be wrong

Sloped aquascapes and deep planted areas can use more substrate than a flat average depth.
Rocks, wood, and decor displace substrate and water volume.
Some livestock need specific substrate types or depths that a volume calculator cannot decide.

FAQ

How deep should aquarium substrate be?

Many aquariums use roughly 2-5 cm; planted tanks often use deeper substrate depending on plant choice.

Why does density matter?

The same volume of sand, gravel, and aquasoil can weigh different amounts.

Substrate depth depends on livestock, plants, and tank design. Check species-specific requirements.