A hidden underground shelter for aquariums and terrariums

The Mossari Under Gravel Cave creates a secure underground shelter beneath aquarium gravel, sand, aquasoil, soil, coco fiber, or other enclosure substrate.

Originally designed as an under-gravel Corydoras cave, its wider interior and open access points also make it suitable as a tarantula burrow, reptile hide, leopard gecko shelter, and underground retreat for other small enclosure animals.

Unlike a conventional cave that sits on top of the substrate, this shelter is designed to disappear beneath it. Only the two upper access openings remain visible, creating a natural-looking hidden space without occupying unnecessary room above the substrate.

Designed for established aquariums

The open-bottom design makes installation possible without removing large sections of substrate or dismantling an established aquascape.

1. Position the cave against the aquarium’s front glass.
2. Press it downward into the existing substrate.
3. Insert a siphon or gravel-vacuum hose through one of the upper openings.
4. Remove the substrate trapped inside the cave.
5. Leave the two upper openings slightly above the substrate.

This creates an open underground chamber while disturbing only the substrate located inside the cave.

The two upper openings remain connected to the main shelter and can be used by fish as additional entrances and exits. Their open-front design also helps animals move freely between the upper openings and the primary underground chamber.

Suitable for

• Corydoras and cory catfish
• Small bottom-dwelling aquarium fish
• Tarantulas
• Terrestrial invertebrates
• Leopard geckos
• Small lizards
• Juvenile or appropriately sized snakes
• Naturalistic terrariums and vivariums
• Bioactive enclosures
• Planted aquariums and aquascapes

Always compare the cave dimensions with the adult size of your animal before ordering. The animal should be able to enter, turn, and exit comfortably.

Available sizes

Medium

• Length: 7.5 inches
• Width: 2.3 inches
• Height: 1.75 inches

Large

• Length: 9.8 inches
• Width: 3.1 inches
• Height: 2.25 inches

Key features

• Buried aquarium or terrarium shelter
• Open-bottom construction
• Two upper access openings
• Large connected interior chamber
• Can be installed in an established aquarium
• Minimizes substrate disturbance during installation
• Textured exterior blends into gravel and naturalistic substrates
• Low-profile design preserves usable enclosure space
• Suitable for aquatic and terrestrial setups
• 3D printed from aquarium-safe PETG
• Designed and made by Mossari

Aquarium installation

Place the cave against the front aquarium glass and press it into the gravel, sand, or aquasoil. Use an aquarium siphon through the upper openings to remove substrate from inside the shelter.

Keep both upper openings exposed slightly above the substrate. Do not completely bury or obstruct them.

Terrarium installation

Place the cave directly on the enclosure floor before adding soil, coco fiber, sand, or another appropriate substrate. Pack substrate around and over the shelter while leaving the access openings clear.

Depending on the animal and enclosure design, the cave may be partially buried or almost completely concealed.

Material and care

The cave is 3D printed from PETG, a durable material suitable for freshwater aquarium use.

Rinse before installation. Clean with water and a soft brush when necessary. Avoid harsh household chemicals, abrasive cleaning tools, and direct contact with high-temperature heating equipment.

Minor layer lines and small surface variations are normal characteristics of the 3D-printing process.

Listing includes one under-gravel cave. Animals, aquarium, terrarium, plants, substrate, and other decorations are not included.

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Under Gravel Cory Cave & Tarantula Reptile Hide | Mossari

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