How to Set Up a Bioactive Enclosure: Layers, Depths and the First Week

The short version: line or seal the base so it holds water, add a 2-inch drainage layer and a mesh barrier only if the substrate maker calls for one (tropical setups with automatic misting), lay at least 2.5 to 3 inches of a bioactive substrate moistened to the maker's instructions, add rock, wood and plants, cover with about half an inch of leaf litter, seed it with springtails and isopods, then run it for a week before the animal goes in. After that you still spot clean, stir the surface and top up leaf litter; bioactive is not maintenance free.

The layer depths and moisture levels below come from the substrate makers' own setup instructions (The Bio Dude and Josh's Frogs), and the safety and husbandry points from the Merck Veterinary Manual, the RSPCA and the New South Wales code. Ask a reptile veterinarian about your own animal's needs.

The layers at a glance

Bioactive layers from bottom to top

Layer	Depth	When you need it	Source
Liner or sealed base	Not applicable	Any enclosure whose maker says it is not watertight	Zen Habitats FAQ; maker listings
Drainage layer (clay balls)	2 in	Tropical substrate with automatic misting; very humid builds	Josh's Frogs; The Bio Dude
Mesh barrier	Not applicable	Always over a drainage layer	Josh's Frogs; The Bio Dude
Bioactive substrate	At least 3 in (The Bio Dude); 2.5 to 3 in (Josh's Frogs)	Always	The Bio Dude; Josh's Frogs
Leaf litter	About 1/2 in	Always	The Bio Dude
Springtails and isopods	One culture of each to start	Always	The Bio Dude

1. Start with an enclosure that holds water

Damp soil sits against the base for years, so the base has to be watertight. Glass terrariums from Exo Terra and REPTI ZOO usually come with watertight bottoms. Zen Habitats says its PVC enclosures are not water tight and sells a fitted Bio-Basin liner (Zen FAQ), and other frame-and-panel enclosures tell you in their listings to seal the bottom with silicone. Check that the substrate barrier is taller than the layers you plan. Our best bioactive enclosures guide lists each enclosure's depth.

2. Decide whether you need a drainage layer

Many setups do not. The Bio Dude says its Terra Sahara (arid) needs no drainage layer and its Terra Firma needs none "90% of the time," with a porous drainage layer, never loose rock, only in very high humidity enclosures (The Bio Dude). Josh's Frogs says its Tropical BioBedding needs no drainage layer with light or hand misting, but with automatic misting it calls for a 2-inch false bottom and a substrate barrier (Josh's Frogs).

If you need one, use a clay drainage medium such as expanded clay balls or The Bio Dude's HydroGrow V2, which the maker says to rinse before use and which "MUST be used with a screen divider" (The Bio Dude). Keep it under the barrier: the Merck Veterinary Manual warns that gravel and pebbles are hard to clean and can cause gastrointestinal obstruction if a terrestrial reptile eats them (Merck).

3. Lay the barrier

The barrier is a sheet of fine mesh cut to the floor and laid on top of the drainage layer, so the soil stays above the water line and does not wash down into the clay. Josh's Frogs and The Bio Dude both call for one whenever there is a drainage layer.

4. Moisten and add the substrate

Each maker gives its own moisture test, and getting it right matters more than the brand:

• Terra Sahara (desert): soak in a bucket, then squeeze until it is about 50% saturated but not dripping; lay at least 3 inches (The Bio Dude). The maker says it holds a tunnel when moisture is kept at 25 to 40%.
• Terra Firma (snakes and burrowers): soak and squeeze until saturated but not dripping; at least 3 inches (The Bio Dude).
• Tropical BioBedding: mix the bag, add dechlorinated or RO water until it sticks together when squeezed with no water running out; 2.5 to 3 inches (Josh's Frogs).

Work out how many bags you need with our bioactive substrate calculator, and see the best bioactive substrates for which mix suits your animal's humidity. If you collect soil, sand or leaf litter yourself, the Merck Veterinary Manual recommends oven baking it first to sterilize it.

5. Add rock, wood and the basking spot

Place rock and wood before the leaf litter goes on. For lizards that bask in the open, such as bearded dragons, the New South Wales code asks for a log, rock or platform under the overhead heat source (NSW code), and every heat source runs through a thermostat, screened from the animal and placed at one end to make a gradient (Merck). Add several hides; the RSPCA asks for several for royal pythons.

6. Plant it

The Merck Veterinary Manual says nontoxic plants can help with humidity for the smallest species, but larger animals often damage them, so choose plants that suit both the animal's size and its humidity. The RSPCA describes an ideal crested gecko enclosure as having tall, broad plants that create light and shade (RSPCA).

7. Cover with leaf litter

The Bio Dude seeds a new enclosure with "a generous 1/2 inch layer" of leaves. Leaf litter is food and cover for the cleanup crew and breaks down over time, about 2 to 3 months in tropical setups and 3 to 4 months in arid ones by The Bio Dude's estimate, so plan to add more.

8. Add the cleanup crew

The Bio Dude's instruction is simple: add a culture of springtails and a culture of isopods directly to the enclosure. Springtails feed on molds, fungi and decaying plant material, and isopods mainly on decaying plant material; our cleanup crew guide covers which to choose for a dry or humid setup. Live cultures are sold by invertebrate breeders, not through the links on this page.

9. Run it for a week before the animal goes in

The RSPCA advises setting up the enclosure and running it for a week before introducing a crested gecko. Use that week to check the temperature at both ends and under the basking spot, the humidity, and the timer on the lights, and to let the cleanup crew settle.

Maintenance: what you still do

• Spot clean. The Bio Dude says the substrate needs spot cleaning in the areas the animal uses as a toilet, and the RSPCA says to spot clean waste as soon as it appears.
• Keep waste areas damp. The Bio Dude suggests keeping the substrate damp where the animal defecates so the cleanup crew works there faster.
• Stir and top up. Josh's Frogs says to stir the surface of BioBedding every 1 to 2 weeks; add leaf litter and sphagnum moss as they break down.
• Replace eventually. Josh's Frogs says to replace BioBedding after several years, once it breaks down.
• Clean the glass and decor. The Merck Veterinary Manual says soap and water are generally enough and that phenolic disinfectants are toxic. The RSPCA's crested gecko guidance also recommends a monthly full clean with a reptile-safe disinfectant; ask your reptile veterinarian how to apply that in a planted enclosure.

Checklist

1. Enclosure watertight, or lined or sealed.
2. Drainage layer and barrier only if the substrate maker calls for them.
3. Substrate moistened to the maker's squeeze test and laid to at least the maker's minimum depth.
4. Basking platform under the heat source; every heater on a thermostat.
5. Plants suited to the animal's size and humidity.
6. About 1/2 inch of leaf litter.
7. Springtails and isopods added.
8. Run for a week; check temperatures and humidity before the animal goes in.