Essential Terrarium
Building Supplies

The container is the heart of your terrarium. It needs to be clear — glass or high-quality clear acrylic — so light can reach your plants. The shape, opening size, and whether it has a lid will determine what kind of terrarium you can build.

Open containers (no lid, or wide openings) are best for succulents, cacti, and air plants that prefer lower humidity and good airflow.

Closed containers work beautifully for tropical mosses, ferns, and humidity-loving plants that thrive in a self-sustaining microclimate.

Without proper drainage, water accumulates at the root zone and causes rot — the number one killer of terrarium plants. The drainage layer sits at the base of your container and acts as a reservoir for excess water, away from plant roots.

Aim for a drainage layer of 3–5 cm for most terrariums, more for larger builds. The material doesn't need to be pretty since it sits at the bottom, but choosing a decorative pebble can look lovely if your container is clear.

Activated charcoal (also called activated carbon) is essential for closed terrariums and highly recommended for open ones. It works by binding to toxins, bacteria, and odour-causing compounds in the soil and water, preventing the build-up that can turn a healthy ecosystem stagnant.

Even a thin layer (1–2 cm) placed above the drainage layer and below the substrate makes a significant difference. For closed terrariums especially, it can mean the difference between a thriving ecosystem and a smelly, algae-ridden one.

Moss is one of the most versatile supplies in your terrarium toolkit. It serves multiple roles: as a barrier layer between drainage and substrate, as a decorative surface cover, and as a living plant in its own right.

Sphagnum moss (dried) is used as a separator layer — it prevents fine soil particles from washing down into the drainage layer and clogging it. It also retains moisture and releases it slowly.

Sheet moss / cushion moss (live or preserved) is used as a surface covering, adding that lush, forest-floor look. Live mosses in a closed terrarium can actually grow and spread over time.

Reindeer moss (usually preserved/dyed) is popular for open terrariums and decorative displays. It doesn't grow but keeps its texture beautifully.

The substrate is where your plants live, and getting it right is critical. Standard potting mix is usually too dense and retains too much moisture for most terrariums. You need a mix that drains freely, resists compaction over time, and provides appropriate nutrients for your chosen plants.

For closed terrariums, the lid is what creates and maintains the miniature water cycle that makes them so low-maintenance. Water evaporates from the soil, condenses on the glass, and drips back down — a self-sustaining loop.

The lid doesn't have to be airtight for most plants. In fact, slightly imperfect seals allow a little fresh air exchange, which many tropical species appreciate.

For jar-style terrariums, a rubber-sealed Kilner lid creates an excellent seal. You can always crack it open for 30–60 minutes a day if condensation becomes excessive.