Clay Pebbles for Terrariums – Natural Drainage Layer

THE BIT AT THE BOTTOM THAT KEEPS EVERYTHING ELSE HAPPY

Nobody admires a terrarium for its drainage layer. But beneath the moss, these little clay pebbles do one of the most important jobs in the whole build: giving excess water somewhere to go, so your moss and plants aren't left sitting in it.

Our natural expanded clay pebbles are made by firing clay in a rotary kiln at over 2,000°F, which puffs each piece into a light, round, porous pebble. They're clean, reusable and suitable for terrariums, mossariums and houseplant pots.

WHY USE CLAY PEBBLES?

Terrariums and most decorative containers have no drainage hole, so any water that isn't taken up by the soil collects at the bottom. A layer of clay pebbles creates a reservoir beneath the growing medium, with air pockets between the pebbles, helping to keep roots and moss out of standing water.

It won't rescue a terrarium that's being overwatered, but it gives your build a much more forgiving foundation. (Here's how the closed-terrarium water cycle works.)

HOW TO USE THEM

1. Add a layer of clay pebbles to the base of your container — around 2–3cm is plenty for most small terrariums.
2. Sprinkle over a thin layer of activated charcoal.
3. Add sphagnum moss or another layer separator to stop soil washing down into the pebbles.
4. Add your terrarium soil, moss and suitable plants.

For the full build, follow our step-by-step moss terrarium guide. Or, if you'd like all the layers in one go, our DIY Terrarium Starter Kit includes drainage, charcoal, sphagnum and soil.

HOW MUCH DO I NEED?

• Small bag (500g) — enough for around 1–3 terrariums
• Large bag (900g) — enough for around 3–5 terrariums

The exact number depends on the width of your containers and how deep you make the drainage layer.

FREQUENTLY ASKED QUESTIONS

Do I need a drainage layer in a closed terrarium?

It's strongly recommended. With no drainage hole, excess water has nowhere else to go, and a drainage layer keeps it away from the soil and roots.

Should I rinse the pebbles before use?

A quick rinse removes any clay dust and keeps the glass looking clean. Let them drain before adding them to your terrarium.

Can I use them for houseplants too?

Yes. They work well as a drainage layer in pots, as a top dressing, or mixed into a chunky aroid substrate.

Can they be reused?

Yes. Clay pebbles don't break down, so they can be rinsed and reused in future builds.

Freshly packed in Bristol by The Moss Fairy. Free UK delivery. International delivery calculated at checkout.