Terrarium What To Put In – The Ultimate Guide To Building A Thriving

To build a thriving terrarium, you need specific layers: a drainage layer (LECA or gravel), a barrier (sphagnum moss), activated charcoal for filtration, and a suitable substrate. Complement these with humidity-loving plants for closed setups or drought-tolerant species for open designs, plus decorative hardscape and optional beneficial microfauna like springtails.

As aquarium enthusiasts, we often marvel at the delicate balance and vibrant life contained within a glass box. It’s a passion that extends beautifully to the world of terrariums, offering a similar joy of creating a miniature, self-sustaining ecosystem right on your desk or windowsill.

For those of us who appreciate the serenity of aquatic life, diving into the terrestrial equivalent – a terrarium – is a natural progression. It’s a fantastic way to bring lush greenery indoors, creating a living piece of art with surprisingly low maintenance once established.

If you’ve been wondering terrarium what to put in to create one of these captivating biomes, you’re in the right place. In my experience, the secret to a successful terrarium lies in thoughtful planning and selecting the right components.

This comprehensive guide will walk you through every essential element, from the foundational layers to the living inhabitants and aesthetic touches, ensuring your miniature world thrives.

Laying the Foundation: Essential Terrarium Layers

Just like setting up an aquarium, the success of your terrarium hinges on a well-constructed foundation. These layers work together to manage water, provide nutrients, and create a healthy environment for your plants.

Skipping or improperly assembling these crucial layers is a common mistake that can lead to root rot and a failing terrarium.

Drainage Layer: Preventing Waterlogging

The very first layer in almost any terrarium is the drainage layer. Its primary purpose is to collect excess water, preventing it from saturating the soil and suffocating plant roots.

Without adequate drainage, moisture can build up, leading to anaerobic conditions and eventually root rot, which is fatal for most terrarium plants.

For this layer, I highly recommend using a material like small gravel, lava rock, or even better, a LECA drainage layer. LECA (Lightweight Expanded Clay Aggregate) is particularly effective because it’s porous, lightweight, and offers excellent aeration.

Aim for a depth of about 1 to 2 inches, depending on the size of your container. This will provide sufficient space for water accumulation without compromising the overall aesthetic or plant growth.

Pro Tip: When I first started building terrariums, I often underestimated the importance of the drainage layer. I’ve noticed that using a LECA drainage layer not only provides superior water management but also makes the terrarium lighter and easier to move. It’s a small detail that makes a big difference in long-term success.

Barrier Layer: Separating Drainage from Substrate

Directly above your drainage layer, you’ll need a barrier. This layer is crucial for preventing your substrate (soil) from mixing with the drainage material.

If the soil mixes with the drainage, it can clog the spaces meant for water collection, rendering the drainage layer ineffective.

A simple piece of fine mesh screen, landscape fabric, or even a layer of long-fiber sphagnum moss works perfectly here. I personally prefer sphagnum moss for its natural look and ability to help regulate moisture.

Ensure the barrier completely covers the drainage layer, extending slightly up the sides of the container if possible. This creates a clear separation and maintains the integrity of each layer.

Activated Charcoal: The Odor and Toxin Fighter

Often overlooked by beginners, a thin layer of horticultural activated charcoal is a game-changer for closed terrariums. This layer acts as a natural filter, absorbing odors and toxins that can build up in a sealed environment.

It helps keep the air inside fresh and prevents unpleasant smells, which can sometimes occur from decomposing organic matter.

A half-inch layer of activated charcoal filtration, placed directly on top of your barrier, is usually sufficient. Make sure to use horticultural charcoal, not barbecue charcoal, as the latter often contains chemicals harmful to plants.

This small addition significantly contributes to the longevity and health of your miniature ecosystem.

Substrate Layer: The Heart of Plant Growth

The substrate is where your plants will root and draw nutrients, making it one of the most critical layers. The type of substrate you choose will depend heavily on the plants you plan to include.

For most tropical terrarium plants, a high-quality, well-draining terrarium soil mix is ideal. This often includes components like coco fiber, perlite, vermiculite, and a small amount of compost.

I find that a mix incorporating peat moss or a good quality sphagnum moss substrate provides excellent moisture retention while still allowing for aeration. The depth of this layer should be at least 2-3 inches, providing ample room for plant roots to establish and grow.

For succulents or cacti in open terrariums, a specialized sandy, fast-draining mix designed for arid plants is essential. Always match your substrate to your plants’ specific needs.

Choosing the Right Plants for Your Terrarium

Selecting the right plants is perhaps the most exciting part of building your terrarium. The key to success is choosing species that thrive in similar conditions, particularly regarding humidity and light.

Mixing plants with vastly different requirements is a recipe for disappointment. Always consider the ultimate size of the plant, its growth rate, and its specific environmental needs.

For Closed Terrariums (High Humidity)

Closed terrariums create a self-contained, high-humidity environment, perfect for plants that love tropical conditions. These plants often have specific moisture requirements that are easily met within a sealed system.

Excellent choices include miniature ferns like ‘Lemon Button’ fern, various mosses, and small foliage plants.

Some of my personal favorites are Fittonia albivenis (Nerve Plant) with its striking vein patterns, and Pilea involucrata (Friendship Plant) for its beautiful textured leaves. Both remain relatively small and appreciate the consistent humidity.

Mosses are also fantastic for closed terrariums, offering a lush green carpet. You can even use aquatic mosses like Java moss emersed, which adapts beautifully to humid terrestrial conditions.

For more ideas, check out our guide on closed terrarium plants list.

For Open Terrariums (Lower Humidity)

Open terrariums, by contrast, are ideal for plants that prefer drier conditions and good air circulation. These usually have wide openings, allowing for air exchange and preventing humidity buildup.

Succulents and cacti are the undisputed stars of open terrariums. Their ability to store water makes them perfect for environments where watering is less frequent.

Small varieties of Echeveria, Haworthia, and even miniature aloe plants work wonderfully. Air plants (Tillandsia species) are also excellent choices, as they don’t require soil and can be simply placed on decorative elements.

Remember that even drought-tolerant plants need some moisture, just far less frequently than their tropical counterparts.

Common Mistake: One of the most frequent errors I’ve seen with open terrariums, especially those featuring succulents, is overwatering. People often treat them like tropical plants, leading to root rot. For succulents, always let the soil dry out completely between waterings, which might be only every few weeks!

Decorative Elements: Bringing Your Terrarium to Life

Once your essential layers and plants are in place, it’s time to add the artistic touches that make your terrarium truly unique. Decorative elements not only enhance the visual appeal but can also provide microclimates or perches for plants.

Think about creating a miniature landscape, complete with hills, valleys, and focal points.

Hardscape: Structure and Visual Interest

Hardscape refers to the non-living elements that provide structure and visual interest. In a terrarium, this often includes rocks, stones, and wood.

Pieces of interesting rock formations, polished river stones, or rough slate can add texture and define pathways or seating areas for your miniature world.

Manzanita driftwood is a fantastic choice for terrariums. Its intricate, smooth branches create a natural, sculptural element, reminiscent of ancient trees or fallen logs in a tiny forest.

Always ensure any hardscape elements are clean and free of pests or chemicals before adding them to your terrarium.

Softscape & Other Accents

Beyond the hardscape, softscape elements and small accents can further personalize your terrarium. Live or preserved mosses can be tucked around rocks and wood to create a lush, natural ground cover.

Consider small, inert figurines – perhaps a tiny gnome, a miniature bench, or a small animal – to add a whimsical touch. Just make sure they are made of non-toxic materials that won’t degrade or leach chemicals into the terrarium environment.

These elements are where your creativity can truly shine, transforming a collection of plants into a captivating scene. If you’re looking for inspiration, exploring DIY terrarium ideas can spark some amazing designs.

The Unseen Heroes: Microfauna and Equipment

While plants and decor are the stars, a truly thriving terrarium often benefits from a supporting cast of tiny helpers and appropriate equipment. These elements contribute to the long-term health and stability of your miniature ecosystem.

They address aspects like biological breakdown and essential environmental controls.

Custodian Critters (Optional but Recommended)

For closed terrariums, introducing a small “clean-up crew” of microfauna can be incredibly beneficial. These tiny invertebrates act as nature’s recyclers, breaking down decaying plant matter and preventing mold growth.

A thriving springtail culture is my top recommendation. Springtails are tiny, harmless arthropods that feed on mold and fungus, keeping your terrarium clean and healthy.

Isopods (dwarf white or powder blue varieties) are another excellent choice, especially for larger terrariums, as they also consume decaying organic material. These custodian critters help maintain the biological balance, reducing the need for manual cleaning.

Lighting Solutions: Powering Photosynthesis

All plants need light for photosynthesis, and terrariums are no exception. While indirect natural light can work, supplemental lighting is often necessary, especially if your terrarium is not near a bright window.

A high-quality full spectrum LED fixture is ideal for terrariums. These lights provide the necessary wavelengths for healthy plant growth without generating excessive heat, which can be detrimental in a closed system.

Position the light above your terrarium, ensuring it provides even coverage. A timer set for 8-12 hours a day will help establish a consistent photoperiod, mimicking natural daylight cycles.

Misting and Humidity Control

Maintaining appropriate humidity is crucial, especially for closed terrariums with tropical plants. While closed systems recycle moisture, they may still need occasional top-ups.

A simple spray bottle filled with dechlorinated water is perfect for manual misting. For larger or more elaborate setups, a small misting system emitter can provide automated, consistent humidity, which is especially useful for humidity-loving plants.

For open terrariums, misting is generally not required and can even be harmful to succulents and cacti. Always assess your plants’ needs and the terrarium’s environment before adding moisture.

Terrarium Layering & Plant Selection Decision Table

To help you decide exactly terrarium what to put in, this table outlines the ideal components based on whether you’re building a closed or open terrarium.

Component	Closed Terrarium (High Humidity)	Open Terrarium (Low Humidity)
Drainage Layer	LECA, lava rock, coarse gravel (1-2 inches)	Small amount of gravel (optional, <1 inch)
Barrier Layer	Sphagnum moss, fine mesh screen	Fine mesh screen (if drainage used)
Activated Charcoal	Horticultural charcoal (0.5 inch layer)	Not typically required
Substrate Layer	Tropical terrarium mix (peat, coco fiber, perlite)	Cactus/succulent mix (sandy, fast-draining)
Plant Types	Fittonia, Pilea, small ferns, mosses, miniature orchids	Succulents, cacti, air plants (Tillandsia)
Hardscape	Manzanita driftwood, smooth river stones, lava rock	Decorative rocks, petrified wood, sandy elements
Microfauna	Springtails, isopods (recommended)	Not applicable
Lighting	Indirect natural light or full spectrum LED fixture	Bright indirect natural light or full spectrum LED fixture
Humidity Control	Misting as needed, occasional open for air exchange	Minimal to no misting

Bringing It All Together: Assembly Tips and Maintenance

Once you’ve gathered all your chosen components, the assembly process is relatively straightforward. Start by thoroughly cleaning your glass container to ensure it’s free of residues.

Layer your materials carefully, starting with drainage, then barrier, charcoal, and finally the substrate. For a detailed step-by-step, our guide on how to make a terrarium for beginners offers excellent guidance.

When planting, gently remove plants from their nursery pots, shaking off excess soil if needed. Create small depressions in the substrate, place your plants, and gently pat the soil around their roots.

Arrange your decorative elements, step back, and admire your miniature landscape. Initial watering should be light, especially for closed terrariums, to avoid over-saturating the substrate.

Long-term maintenance for closed terrariums is minimal; you might only need to mist every few weeks or months, and occasionally prune overgrown plants. Open terrariums require more frequent, but still sparse, watering.

Common Terrarium Mistakes to Avoid

Even with the best intentions, it’s easy to make a few missteps when building and maintaining your first terrarium. Being aware of these common pitfalls can save you a lot of frustration.

Here are some of the most frequent mistakes I’ve encountered:

• Overwatering: This is by far the biggest killer of terrarium plants, especially in closed systems. Less is truly more. If you see condensation constantly dripping or the soil looks soggy, it’s too wet.
• Wrong Plant Choices: Mixing plants with vastly different light and humidity needs will inevitably lead to some plants suffering. Always choose plants that thrive in similar conditions.
• Inadequate Drainage: As discussed, a poor or absent drainage layer leads to waterlogged soil and root rot. Don’t skip this critical step.
• Too Much Direct Sunlight: While plants need light, direct, intense sunlight can quickly overheat a closed terrarium, essentially cooking the plants inside. Bright, indirect light is always best.
• No Air Circulation (for closed terrariums): While closed terrariums are sealed, it’s good practice to open them for a few minutes once a week or every couple of weeks. This allows for some air exchange and prevents stagnant air.

Frequently Asked Questions About Terrariums

Can I put fish in a terrarium?

Generally, no. A typical terrarium is a terrestrial environment designed for plants and possibly small invertebrates. If you’re thinking of combining aquatic and terrestrial elements, you’re likely envisioning a paludarium or aquaterrarium, which are specialized setups requiring specific filtration and water features not present in a standard terrarium.

How often do I water a terrarium?

The watering frequency depends entirely on the type of terrarium. Closed terrariums might only need watering every few weeks or even months, as they recycle their own moisture. Open terrariums, especially those with succulents, should only be watered when the soil is completely dry, which could be every 2-4 weeks.

Do terrariums need sunlight?

Terrariums need light, but typically not direct sunlight. Bright, indirect light is ideal. Direct sun can cause a closed terrarium to overheat rapidly, damaging the plants. If natural light isn’t sufficient, a full spectrum LED fixture can provide the necessary illumination for healthy plant growth.

What size container is best for a beginner?

For beginners, a medium-sized container (e.g., a gallon jar or a 6-10 inch wide vessel) is often best. Smaller containers can be harder to balance environmentally, and very large ones can be intimidating. A medium size provides enough space for a variety of plants and makes maintenance more manageable.

Conclusion

Creating your own terrarium is an incredibly rewarding endeavor, a journey from a simple glass container to a vibrant, living microcosm. Just like with our beloved aquariums, the key lies in understanding the specific needs of the ecosystem you’re trying to build.

By carefully selecting what to put in your terrarium – from the essential drainage layer and rich substrate to the perfect plants and subtle decorative touches – you’re setting the stage for long-term success. Remember, each component plays a vital role in the overall health and beauty of your miniature world.

With this guide in hand, you’re well-equipped to embark on your terrarium adventure. Enjoy the process of designing, planting, and watching your tiny ecosystem flourish. It