Quick answer: Safe bioactive terrarium materials include cork bark, hardwoods sold for terrarium use (spiderwood, grapewood, mopani, driftwood), inert stones, 100% silicone without mould inhibitors, and rinsed, pesticide-free plants. Avoid aromatic softwoods like cedar and pine, treated, painted or varnished wood, construction adhesives, silicone with fungicides, metallic or crumbling rocks, and anything collected outside that you have not cleaned. Amphibians and invertebrates are the most sensitive, so be strictest with frog and crew-heavy builds.
Everything inside a bioactive enclosure is in close, constant contact with the animal, the plants and the clean-up crew, usually in warm, humid conditions that speed up leaching and decay. A material that is harmless on a shelf can release resin, oils or chemicals once it is warm and damp for months. This page covers material safety only; for how the materials fit together, see the master guide on how to set up a bioactive terrarium.
Why material safety matters more in bioactive builds
- Amphibians absorb through their skin. Dart frogs, tree frogs and salamanders take up chemicals directly from surfaces and water.
- The crew is sensitive. Springtails and isopods are invertebrates, and many common insecticides are designed to kill exactly that kind of animal.
- Heat and humidity speed up leaching. Resins, tannins, oils and chemical residues come out faster in a warm, wet enclosure.
- Nothing gets replaced. In a non-bioactive enclosure, substrate is changed often. In a bioactive one, materials stay in place for years.
Wood
| Generally safe | Avoid |
|---|---|
| Cork bark (flats, tubes, rounds, branches) | Cedar (aromatic oils are a known irritant) |
| Spiderwood and other azalea root woods | Pine, spruce, fir and other resinous softwoods, unless fully cured and sealed by a reputable supplier |
| Grapewood | Pressure-treated, painted, stained or varnished wood |
| Mopani and Malaysian driftwood | Plywood, MDF, particle board and other glued composites |
| Manzanita | Wood from unknown sources, near roads or sprayed areas |
Cork bark is the easiest choice for humid builds: it is light, naturally rot-resistant and very hard to go wrong with. Browse cork bark for hides, backgrounds and climbing. Hardwoods such as mopani and Malaysian driftwood are dense and long-lasting, but release tannins that can tint water brown at first; soaking reduces this. Softer woods may rot in constant humidity, which is not toxic but does mean replacing them.
Even wood sold for terrarium use benefits from a scrub and rinse before use. The full method is in how to clean and prepare wood for a terrarium, and a comparison of species is in best woods for a terrarium.
Stone and rock
| Generally safe | Use with care or avoid |
|---|---|
| Slate, granite, quartz, basalt and lava rock | Rocks with visible metal veins or ore (possible heavy metals) |
| Seiryu stone (calcium-bearing; fine in terrariums) | Crumbling, flaking or sandy rocks that break down when wet |
| Feather rock and moon rock | Painted, dyed or coated decorative stones |
| Rocks sold for aquarium or terrarium use | Rocks with sharp edges in reach of animals |
Calcium-bearing stones such as limestone and seiryu stone are fine in a terrarium. They only matter in aquariums or water features with soft-water species, because they slowly raise hardness. To test an unknown rock, drip on some vinegar: fizzing means calcium carbonate.
Physical safety matters as much as chemistry. Place heavy stones directly on the enclosure floor or barrier, never on top of soil, so burrowing animals cannot dig underneath and be crushed. Stacked stones should be siliconed together. More on this in using rocks and stone in a bioactive terrarium.
Silicone, glue and foam
Silicone
Use 100% silicone sealant labelled aquarium-safe, or one confirmed to contain no mould inhibitors, fungicides or anti-mildew additives. Bathroom and kitchen silicones usually contain these and are not suitable. Let silicone cure fully, typically 24–48 hours for thin beads and longer for thick ones, and air the enclosure until the vinegar smell is gone before adding animals.
Expanding foam
Many keepers build backgrounds from expanding polyurethane foam, usually a version sold for ponds and water features. Once fully cured and covered with silicone and substrate or cork, it is widely used safely. Let it cure completely, trim it and cover exposed foam, since some animals will chew bare foam.
Adhesives to avoid
Avoid construction adhesives, solvent-based glues and spray adhesives inside the enclosure. Cyanoacrylate (super glue) gel is commonly used to attach plants and moss to wood and is considered safe once cured, but use small amounts.
Plants and pesticides
Nursery plants are the most common way harmful chemicals get into a bioactive enclosure. Commercial growers often use insecticides, including systemic types that are taken up into the plant tissue and persist for weeks or months. These can kill springtails and isopods and are a risk to amphibians.
How to make plants safer
- Buy from growers who sell for vivarium use where possible, and ask about pesticide use.
- Remove the plant from its pot and wash away as much nursery soil as practical.
- Rinse leaves and roots thoroughly under lukewarm water.
- Repot in clean substrate and grow it out separately for several weeks before adding it to an enclosure with animals.
- Avoid plants with visible fertiliser beads in the soil.
Plant toxicity
Many popular terrarium plants, including pothos and philodendron, contain calcium oxalate, which irritates the mouth if eaten. They are widely used with insectivores such as crested geckos and dart frogs that do not eat plants. For herbivores and omnivores like tortoises, bearded dragons and blue-tongued skinks, choose plants known to be safe to eat. See the reptile-safe plants toxicity guide, and use the bioactive plant planner to filter suitable plants.
Substrates and soil
- Safe: purpose-made bioactive mixes such as Jurassic ABG Terrarium Mix, plain coco fibre, cypress mulch, sphagnum moss and leaf litter sold for terrarium use.
- Avoid: garden soil, compost, potting soils with fertiliser or perlite, cedar or pine shavings, and aromatic wood mulches.
- Leaf litter: buy dried leaves prepared for terrarium use, such as those in our tropical leaf litter range, or collect from unsprayed areas and clean them.
Materials collected outside
Collecting leaves, wood and stone yourself is tempting, and in many parts of Canada oak and maple leaves are everywhere in autumn. It can be done safely, but carries real risks: pesticide and herbicide drift, road salt and vehicle residue, pests and parasites, and wild invertebrates such as mites or predatory insects.
- Collect only from areas you know are not sprayed, away from roads, farms and lawns.
- Never collect from parks or protected areas where removal is prohibited.
- Rinse thoroughly, then heat-treat. Leaves and small wood pieces are commonly baked at a low oven temperature, around 90–120 °C, until dry, watching carefully to avoid scorching. Larger wood can be scrubbed and soaked or boiled where it fits.
- Rocks can be scrubbed and boiled. Do not bake rocks, as trapped moisture can make some crack or burst.
- Never collect native animals, including insects and amphibians, for your enclosure.
Cleaning products around the enclosure
- Clean glass with plain water or diluted white vinegar, not ammonia-based glass cleaners.
- Do not use air fresheners, scented candles, insect sprays or flea treatments near the enclosure.
- Wash hands before working in the enclosure, especially after using lotions or handling chemicals.
Signs something unsafe is in the enclosure
- A sudden crash in springtails and isopods after adding a new plant or item.
- Lethargy, loss of appetite, unusual posture or skin changes in the animal.
- Strong chemical, resin or solvent smells.
Remove the most recent addition first, increase ventilation and, if the animal shows symptoms, contact a reptile or amphibian veterinarian. Other build errors that look similar are covered in bioactive terrarium mistakes to avoid, and a full shopping list of safe supplies is in the bioactive supplies checklist.
FAQ
Is pine wood safe for a terrarium?
Raw pine and other resinous softwoods are generally avoided, because their resins and aromatic compounds can irritate reptiles and amphibians, especially in warm, humid conditions. Stick to cork and hardwoods sold for terrarium use.
What silicone is safe for terrariums?
Use 100% silicone that is labelled aquarium-safe or confirmed to contain no mould inhibitors or fungicides. Let it cure completely, usually 24–48 hours or more, and air the enclosure until the vinegar smell is gone.
Can I use sticks and leaves from my backyard?
You can if your yard is not treated with pesticides or herbicides, but clean and heat-treat everything first, and expect some risk of introducing pests. Purchased, prepared materials are the safer option for sensitive animals such as dart frogs.
Are pothos and philodendron toxic to reptiles?
They contain calcium oxalate, which irritates if chewed. They are widely used with insect-eating animals such as crested geckos and frogs that do not eat plants, but should be avoided with herbivores like tortoises and bearded dragons.
How long should I quarantine new plants?
Several weeks is a sensible minimum after washing off nursery soil and repotting. This lets any pesticide residue break down and gives you time to spot pests before the plant goes in with your animal and crew.