Aquarium Substrate Calculator
How much gravel or sand do you need? Enter your tank's footprint and desired depth â we'll tell you the weight to buy.
Calculate substrate amount
Based on typical gravel density (~1.6 kg/L). Fine sand packs denser â buy ~10% less sand than the gravel estimate.
How much substrate per gallon?
The quick rule: 1â2 lbs of substrate per gallon of tank capacity. A 20-gallon tank needs about 20â40 lbs of gravel for 1â2 inches of coverage. This calculator is more precise because it uses your actual tank footprint instead of the rough per-gallon rule.
Recommended depths
| Tank type | Depth | Notes |
|---|---|---|
| Standard community | 1â2 in | Easy to clean, enough for decor |
| Planted tank | 2â3 in | Roots need anchoring depth |
| Cichlid / diggers | 1â1.5 in | They'll rearrange it anyway |
| Shrimp / nano | 0.75â1 in | Active soils buffer water chemistry |
Gravel vs. sand
- Gravel: easy to vacuum, comes in many colors, good for most community tanks.
- Sand: natural look, required for bottom-dwellers like corydoras and loaches (gravel can injure their barbels), but compacts more and needs gentle cleaning.
- Plant substrates: nutrient-rich soils for planted tanks; they exhaust after 1â2 years and cost more.
Pro tip: slope the substrate â 1 inch at the front, 2â3 inches at the back. It adds visual depth and gives plants more root room where it matters.
Frequently asked questions
How much gravel for a 20 gallon tank?
About 20â40 lbs for 1â2 inches of depth. A 20-gallon long (30Ã12 in footprint) needs roughly 25 lbs for 2 inches.
How deep should aquarium gravel be?
1â2 inches for most tanks, 2â3 inches for planted tanks. Avoid going over 3 inches with fine material, which can trap waste.
Do I need to wash substrate before adding it?
Yes â rinse gravel and sand thoroughly until the water runs clear, or your tank will stay cloudy for days. Bagged "pre-washed" products still benefit from a quick rinse.