Aquarium substrate calculator

Measure the inside length and width of the tank, decide how deep you want the bed, then multiply: length × width × depth = volume. Multiply that volume by the density of the material to get weight. Our aquarium substrate calculator does it for you in inches or centimetres and returns pounds, kilograms, litres and the number of bags to buy.

As a starting point, use 1–2 inches for a fish-only tank and 2–3 inches for a planted setup. Always buy roughly 10% extra for settling and sloping.

A standard 55 gallon tank has a 48 × 13 inch footprint. With gravel at about 100 lb per cubic foot you need roughly 36 lbs at 1 inch, 72 lbs at 2 inches and 108 lbs at 3 inches.

The old rule of thumb — 1 to 1.5 lbs per gallon — gives you 55 to 82 lbs, which matches a 1.5 to 2 inch bed. Run your exact numbers through the substrate calculator before you shop.

A 20 gallon long measures 30 × 12 inches inside, so the footprint is larger than a standard 20 gallon. You will need about 21 lbs at 1 inch, 42 lbs at 2 inches and 63 lbs at 3 inches of gravel. Sand comes in slightly lighter at around 38 lbs for a 2 inch bed.

Compare tank shapes with the aquarium volume calculator if you are still deciding between a long and a standard footprint.

For most community and fish-only tanks, yes — 4 inches is deeper than you need and it makes vacuuming the bed awkward. Two to three inches is the practical ceiling for gravel.

Four inches becomes reasonable when you are building a planted aquarium with deep-rooting stems such as vallisneria or sword plants, because you need the volume to anchor roots and hold nutrients. If you go deep, slope the bed down towards the front glass so the lowest layer still gets some circulation.

Yes. An overly deep bed compacts, traps fish waste and uneaten food, and can turn anaerobic — the layer that produces hydrogen sulfide gas and a rotten-egg smell. It also cuts into swimming space, adds real weight to the stand, and makes gravel vacuuming slower.

Stay inside the 1 to 3 inch range for gravel and 2 to 4 inches for a dedicated substrate depth in a planted tank, and stir the deeper layers occasionally.

There is no single answer — it depends on the species and on the look you want. Tetras, rasboras, loaches and most cichlids colour up more strongly and settle faster over a dark bed, because it matches the shadows they would hide in in the wild. Bottom feeders such as corydoras and kuhli loaches are often sold on bare or light sand, and they show natural foraging behaviour on a pale, fine substrate.

Light substrate also makes detritus and algae more visible, so it needs more frequent cleaning. Pick the colour for your fish first, then confirm the weight with the sand calculator.

1–2 inches is enough for a fish-only or lightly planted tank. 2–3 inches suits most planted setups, and 3–4 inches is justified for deep-rooting plants or a layered soil-and-gravel bed. Slope it 1 inch higher at the back to create depth in the aquascape.

Our aquarium substrate depth calculator works the other way round: tell it how much material you already own and it tells you how far that spread across your footprint.

No visible bulb colour kills algae. Algae grow when they have light, nutrients and time, and changing the colour of the lamp does not remove any of those three. Blue and actinic light look dramatic but they still grow algae, and green light is simply reflected rather than destroyed.

What actually works is shortening the photoperiod to 6–8 hours, dimming the intensity, feeding less so fewer nutrients reach the water, and adding fast-growing plants or a clean-up crew. If you are setting up a planted tank, size the substrate and lighting together with the aquarium soil substrate calculator.

New tank syndrome — ammonia and nitrite poisoning in an aquarium whose filter has not finished cycling — is the leading cause of fish loss, and it accounts for the majority of first-time deaths. After that come overfeeding and poor water quality, then temperature or pH shock from sudden water changes.

Substrate plays a quiet role: an over-deep bed traps waste and adds to the organic load, so keeping the depth sensible and vacuuming regularly protects water quality. Check your footprint with the volume calculator before dosing water treatments.

A standard 10 gallon has a 20 × 10 inch footprint. Using gravel at 100 lb per cubic foot, you need about 12 lbs for a 1 inch bed, 17 lbs at 1.5 inches and 23 lbs at 2 inches.

The quick "1 lb per gallon" estimate says 10 lbs, but that rule ignores how shallow a 10 gallon actually is — the depth-based figure above is the one to trust. Enter 20 × 10 and your chosen depth in the aquarium substrate calculator for the exact number.

Plan on 2 to 3 inches as a base, rising to 3 or 4 inches at the back. A nutrient-rich aquarium soil substrate lets you go slightly shallower than gravel because every granule feeds the roots, while inert sand and gravel need root tabs to do the same job.

Layering works well: 1.5 inches of soil capped with 1 inch of sand or fine gravel keeps the nutrients in place and stops the water clouding up.

The maths is identical — footprint times depth — but the density changes the answer. Gravel settles at about 100 lb per cubic foot, sand at about 90 lb, and lightweight aquarium soil at roughly 40 lb. The same 2 inch bed in a 40 gallon breeder needs about 75 lbs of gravel but only 30 lbs of soil.

Use the gravel calculator, the sand calculator or the soil calculator so the density matches what is actually in the bag.

Add the front depth to the back depth and divide by two, then treat that average as a uniform layer. A bed that runs 1 inch at the front and 3 inches at the back behaves like a flat 2 inch layer for volume purposes.

Sloping is worth doing: it pushes the focal point up, hides detritus at the front and gives roots more room at the rear. Our substrate depth calculator accepts both the shallow and deep end and works out the average for you.

Convert the weight you need into the bag size sold near you, then round up — 42 lbs of gravel is three 15 lb bags, not two. It is worth buying one extra bag, because settling, sloping and the inevitable uneven patch all cost material.

The calculator returns a bag count for 5, 10, 20 and 25 lb packaging alongside pounds and kilograms, so you can shop straight from the result.

For gravel and sand, yes. Rinse in a bucket of cool tap water, stirring and decanting until the water runs clear — this removes the dust that otherwise clouds the tank for days. A fine sand bed can take five or six changes of water.

Planted soils are the exception: many manufacturers say not to rinse them, because the granules break down and you will wash away the nutrients. Check the bag, then measure the depth you have left with the depth calculator.