The usual rule of thumb, three times the diagonal leg span in width, comes from terrestrial keeping and does not translate well to arboreal species. An arboreal tarantula lives on a vertical plane. What it needs is height, a surface to anchor silk to and enough distance between the retreat and the walls to build a proper tunnel.
The working rule
For an adult arboreal, aim for an enclosure at least four times the leg span in height and about twice the leg span in width and depth. For a spider with a fifteen centimetre leg span that means roughly 30 by 30 by 50 centimetres, which is exactly why the Arboreal Paradise Adult is built to that size.
Why bigger is not automatically better
A young arboreal in a huge enclosure often struggles to find prey, and keepers panic when the spider refuses food for weeks. It is rarely illness. It is a spiderling that cannot locate a cricket four times its body length away. Match the enclosure to the animal now and upgrade when it grows, rather than buying the final size on day one.
The other reason to size sensibly is humidity. A large volume of air over a small patch of damp substrate dries out quickly, and you end up watering constantly to keep the base damp.
When to upgrade
- The spider can touch two opposite walls at once with legs extended.
- The webbed retreat fills more than a third of the enclosure.
- You cannot get a water dish and the retreat in without them touching.
- The cork no longer reaches from the substrate to the upper third.
Any one of those is a reason to move up. Do it after a moult has hardened, not during pre-moult.
Height without a fall risk
Tall enclosures come with one genuine hazard: a heavy adult that falls from the lid onto a hard floor can rupture its abdomen. The fix is not a shorter enclosure, it is filling the vertical space. Cork that reaches most of the way up, a few anchor points for silk and deep, forgiving substrate at the bottom mean there is no long drop onto a bare base.
Sizes at a glance
- Spiderling, under 2 cm: a small vial or 10 × 10 × 15 cm enclosure. Prey needs to be findable.
- Juvenile, 2 to 5 cm: around 15 × 15 × 25 cm.
- Sub-adult, 5 to 8 cm: around 20 × 20 × 30 cm.
- Adult, 8 cm and up: 30 × 30 × 50 cm, which will see most species out for life.
Right now T-LOVER makes the adult size. If you would buy a smaller one, there is a sign-up box on the front page: we build the next size when enough people actually need it.