--- title: Terrarium layers explained | Glass Jar Garden description: The layers of a terrarium, bottom to top: drainage, a barrier, soil and a top dressing. What each does, how deep to make it, and which materials to use. url: https://glassjar.garden/guide/terrarium-layers/ --- Guide # Terrarium layers explained Bottom to top: drainage, a barrier, soil, then a top dressing. Each has one job, and getting the water right between them is most of what keeps a jar alive. - Drainage (LECA or gravel): spare water collects here, away from the roots. - Barrier mesh: stops soil washing down into the drainage. - Soil (a mix like ABG): where roots live. Deep enough for them, usually 5 to 8 cm. - Top dressing (moss, leaf litter, stones): looks good, holds damp, feeds the crew. - Water so the soil is damp, never soggy. Standing water above the drainage rots roots. ## What goes in each layer ### Drainage - [Aquarium gravel](https://glassjar.garden/guide/soils/aquarium-gravel/), holds 7.5 % by volume water - [Decomposed granite](https://glassjar.garden/guide/soils/decomposed-granite/), holds 11.5 % by volume water - [Fine clay pebbles](https://glassjar.garden/guide/soils/clay-pebbles-fine/), holds 16 % by volume water - [Lava rock (scoria)](https://glassjar.garden/guide/soils/lava-rock/), holds 17.5 % by volume water - [LECA (expanded clay)](https://glassjar.garden/guide/soils/leca/), holds 14 % by volume water - [Pea gravel](https://glassjar.garden/guide/soils/pea-gravel/), holds 5 % by volume water - [Perlite](https://glassjar.garden/guide/soils/perlite/), holds 25 % by volume water - [Pumice](https://glassjar.garden/guide/soils/pumice/), holds 27.5 % by volume water - [River pebbles](https://glassjar.garden/guide/soils/river-pebbles/), holds 3 % by volume water ### Barrier - [Substrate barrier mesh](https://glassjar.garden/guide/soils/mesh-barrier/), holds 1 % by volume water ### Filter - [Activated charcoal](https://glassjar.garden/guide/soils/activated-charcoal/), holds 30 % by volume water - [Biochar](https://glassjar.garden/guide/soils/biochar/), holds 37.5 % by volume water - [Horticultural charcoal](https://glassjar.garden/guide/soils/horticultural-charcoal/), holds 25 % by volume water - [Sphagnum barrier layer](https://glassjar.garden/guide/soils/sphagnum-barrier/), holds 70 % by volume water - [Zeolite](https://glassjar.garden/guide/soils/zeolite/), holds 30 % by volume water ### Soil - [ABG mix](https://glassjar.garden/guide/soils/abg-mix/), holds 45 % by volume water - [Akadama](https://glassjar.garden/guide/soils/akadama/), holds 37.5 % by volume water - [Aquasoil](https://glassjar.garden/guide/soils/aquasoil/), holds 40 % by volume water - [Bagged potting soil](https://glassjar.garden/guide/soils/potting-soil/), holds 60 % by volume water - [Calcined clay](https://glassjar.garden/guide/soils/calcined-clay/), holds 35 % by volume water - [Clay](https://glassjar.garden/guide/soils/clay/), holds 45 % by volume water - [Coco coir](https://glassjar.garden/guide/soils/coco-coir/), holds 70 % by volume water - [Coco husk chips](https://glassjar.garden/guide/soils/coco-husk-chips/), holds 27.5 % by volume water - [Horticultural sand](https://glassjar.garden/guide/soils/horticultural-sand/), holds 10 % by volume water - [Orchid bark (fir/pine bark)](https://glassjar.garden/guide/soils/orchid-bark/), holds 30 % by volume water - [Peat-based soilless mix](https://glassjar.garden/guide/soils/peat-based-mix/), holds 57.5 % by volume water - [Pine bark fines](https://glassjar.garden/guide/soils/pine-bark-fines/), holds 37.5 % by volume water - [Rice hulls](https://glassjar.garden/guide/soils/rice-hulls/), holds 20 % by volume water - [Sphagnum peat moss](https://glassjar.garden/guide/soils/peat-moss/), holds 65 % by volume water - [Topsoil](https://glassjar.garden/guide/soils/topsoil/), holds 32.5 % by volume water - [Tree fern fibre](https://glassjar.garden/guide/soils/tree-fern-fiber/), holds 35 % by volume water - [Vermiculite](https://glassjar.garden/guide/soils/vermiculite/), holds 47.5 % by volume water - [Worm castings](https://glassjar.garden/guide/soils/worm-castings/), holds 52.5 % by volume water ### Top dressing - [Aquarium sand](https://glassjar.garden/guide/soils/aquarium-sand/), holds 25 % by volume water - [Black sand](https://glassjar.garden/guide/soils/black-sand/), holds 23 % by volume water - [Cork crumbs](https://glassjar.garden/guide/soils/cork-bits/), holds 15 % by volume water - [Dried long-fibre sphagnum moss](https://glassjar.garden/guide/soils/sphagnum-dried/), holds 55 % by volume water - [Leaf litter](https://glassjar.garden/guide/soils/leaf-litter/), holds 35 % by volume water - [Live sphagnum moss](https://glassjar.garden/guide/soils/sphagnum-live/), holds 65 % by volume water - [Magnolia leaves](https://glassjar.garden/guide/soils/magnolia-leaves/), holds 32.5 % by volume water - [Oak leaf litter](https://glassjar.garden/guide/soils/oak-leaves/), holds 37.5 % by volume water ## How water moves between them - Layers go in damp, at about three quarters of what they hold. - Gravel, LECA or lava rock under the soil catches excess water below the roots. - Water wicks up from a wet drainage layer, and sideways into drier soil. - When water rises into the root zone, roots start to rot. - An as-needed watering tops the soil back up to 92% and no further. - Wilting point: 30% of capacity - Root zone: 3.5 cm - Wicking up peat or coir: 4.5 cm - Sideways spread: 20% of the gap a day Compare the drainage materials in [LECA vs gravel vs lava rock](https://glassjar.garden/guide/drainage-leca-vs-gravel/). [Pour the layers in the simulator](https://glassjar.garden/) ## More terrarium guides - [Closed vs open terrarium: Which to build, and which plants suit each.](https://glassjar.garden/guide/closed-vs-open-terrarium/) - [Best plants for a closed terrarium: Plants that live sealed, easiest first.](https://glassjar.garden/guide/best-plants-for-closed-terrarium/) - [Best moss for a terrarium: Mosses for closed and open jars, and what they grow on.](https://glassjar.garden/guide/best-moss-for-terrarium/) - [Terrarium drainage: LECA vs gravel vs lava rock: Every drainage material side by side.](https://glassjar.garden/guide/drainage-leca-vs-gravel/) - [Mould in a terrarium: Why new jars fuzz, which mould matters, and how to stop it.](https://glassjar.garden/guide/terrarium-mould/) - [Springtails vs isopods: The cleanup crew compared: what each eats and where it lives.](https://glassjar.garden/guide/springtails-vs-isopods/)