Terrarium Substrate Layer Calculator
Calculate the volume and depth of each substrate layer for your terrarium based on container dimensions and terrarium type.
A properly layered terrarium substrate is essential for plant health, drainage, and preventing root rot. Each layer serves a specific purpose, and the proportions depend on your container size and terrarium type (open vs. closed).
Standard Terrarium Layer Structure (bottom to top)
| Layer | Material | Purpose | Typical Depth % |
|---|---|---|---|
| 1. Drainage | Pebbles, LECA, gravel | Prevents waterlogging | 15–20% of total height |
| 2. Separation | Mesh screen or charcoal | Stops soil from sinking into drainage | 2–5% (thin layer) |
| 3. Activated Charcoal | Horticultural charcoal | Filters water, prevents odors | 3–5% |
| 4. Growing Medium | ABG mix, potting soil | Where roots grow | 25–35% |
| 5. Top Dressing | Sphagnum moss, leaf litter | Retains moisture, aesthetics | 5–10% |
Volume Formula
For a rectangular container: Volume (liters) = Length (cm) x Width (cm) x Depth (cm) / 1000
For a cylindrical container: Volume (liters) = pi x Radius^2 (cm) x Depth (cm) / 1000
Each layer’s volume = Total volume x (layer percentage / 100).
Worked Example — 30cm x 20cm x 25cm Closed Tropical Terrarium
Total interior volume = 30 x 20 x 25 = 15,000 cm^3 = 15 liters. Usable height for substrate: roughly 60% of total height = 15 cm.
- Drainage layer (20%): 15 x 0.20 = 3.0 cm deep = 1.8 liters of LECA
- Separation mesh: thin sheet, negligible volume
- Charcoal layer (5%): 15 x 0.05 = 0.75 cm = 0.45 liters of charcoal
- Growing medium (30%): 15 x 0.30 = 4.5 cm = 2.7 liters of ABG mix
- Top dressing (5%): 15 x 0.05 = 0.75 cm = 0.45 liters of sphagnum moss
- Remaining 40% = open air space for plant growth above substrate
Terrarium Type Adjustments
Closed tropical terrariums need thicker drainage layers (20%) because excess moisture cannot evaporate. Open arid terrariums need thinner drainage (10–15%) but deeper growing medium with added perlite or sand for faster drainage. Bioactive vivariums require a deeper substrate overall (at least 7–8 cm of growing medium) to support microfauna like springtails and isopods.
Material Quantities by Weight
| Material | Approximate Density | 1 Liter Weighs |
|---|---|---|
| LECA (expanded clay) | 0.3–0.5 kg/L | ~400g |
| Activated charcoal | 0.2–0.4 kg/L | ~300g |
| ABG mix | 0.4–0.6 kg/L | ~500g |
| Sphagnum moss (dry) | 0.03–0.05 kg/L | ~40g |
| Pea gravel | 1.5–1.7 kg/L | ~1,600g |