Aquarium Substrate Calculator

We calculate the base area of your tank (accounting for shape), multiply by your desired depth, then convert to volume. The weight is calculated using the density of your chosen substrate type. Different substrates have different densities - sand is heavier per volume than gravel, for example.

Gravel: Standard aquarium gravel (2-5mm), ~1.5 lbs per gallon

Sand: Play sand or pool filter sand, ~1.7 lbs per gallon

Fine Sand: Very fine sand (sugar grain size), ~1.8 lbs per gallon

Crushed Coral: Crushed coral or aragonite, ~1.4 lbs per gallon

Aquasoil: Plant substrate (ADA, Fluval, etc.), ~1.2 lbs per gallon

Custom: Enter your own density if you know it

Planted tanks: 2-3 inches (5-7.5 cm) for most plants, 3-4 inches (7.5-10 cm) for deep-rooted plants

Fish-only tanks: 1-2 inches (2.5-5 cm) is usually sufficient

Reef tanks: Often use bare bottom or very thin sand bed (0.5-1 inch / 1-2.5 cm)

Note: Deeper substrate can trap waste and create anaerobic zones. Most tanks work best with 1-3 inches.

Substrate displaces approximately 60% of its volume in water. This means if you add 10 gallons of substrate, you'll lose about 6 gallons of water capacity. This is important for accurate volume calculations when dosing medications or treatments.

Always buy 10-20% more than calculated to account for:

• Sloping substrate (deeper in back, shallower in front)
• Washing and rinsing losses
• Future top-offs as substrate settles
• Uneven tank bottom or decorations

Most substrate bags are sold by weight (lbs or kg), so use our calculator to determine exactly how much you need.

Yes, but calculate each layer separately. For example, if you want 1 inch of gravel topped with 1 inch of sand, calculate each depth separately and add the weights together.

Tips for mixing: Match nutrient levels and pH effects. Many aquascapers layer nutrient-rich soils on the bottom and cap them with decorative gravel or sand.

Be aware that over time, finer substrates will settle to the bottom through larger substrates.

Some aquasoils release particles initially, causing temporary cloudiness. Rinse lightly if the brand recommends it, and fill your tank slowly to minimize disruption. Most cloudiness clears within a few days. Using a plate or bowl to diffuse water when filling helps reduce substrate disturbance.

Quality aquasoil can last several years (3-5 years typically). Inert substrates like gravel and sand can last indefinitely with proper maintenance.

For planted tanks: Over time, nutrient-rich substrates deplete. Instead of full replacement, replenish nutrients with fertilizers or root tabs.

Replace substrate if it becomes heavily compacted, develops persistent anaerobic zones (hydrogen sulfide smell), or if you're redesigning your aquascape.

Yes, but do it carefully to avoid disturbing your fish and beneficial bacteria. Here's how:

• Remove fish to a temporary container if possible, or net them to one side
• Layer the new substrate slowly to avoid stirring debris
• Use a cup or bowl to diffuse water flow when refilling
• Monitor water parameters closely for the next few weeks

If adding aquasoil to an established tank, expect some cloudiness and a temporary ammonia spike. The tank will need to re-cycle partially.

For a sloped look, calculate based on the average depth. If you want 1 inch in front and 3 inches in back, use 2 inches as your depth. For more precision, calculate the front and back separately and average the results.