Equipment
Tortoise UVB Lighting Guide
Updated August 1, 2026
Why UVB matters: Tortoises need UVB to metabolize calcium. Without it, they develop MBD — weak bones, shell deformities, and death. Indoor tortoises need artificial UVB. Outdoor tortoises in direct sun do not.
🏠 Indoor tortoises need UVB
If your tortoise lives indoors, artificial UVB is non-negotiable:
- UVB enables calcium absorption
- Without it, calcium supplements are useless
- MBD develops within months without UVB
- Window glass blocks UVB — even sunny windows don't help
🔦 T5 vs T8
T5 HO (High Output)
- • Stronger UVB output
- • Can be placed 12-18" from tortoise
- • Best for large enclosures
- • Requires T5 fixture
T8
- • Weaker UVB output
- • Must be within 6-12" of tortoise
- • Good for smaller enclosures
- • Standard T8 fixture works
Recommendation: T5 HO 10-12% is the gold standard. Arcadia 12% or Zoo Med ReptiSun 10.0.
🔥 Basking bulbs
Tortoises need a warm basking spot to thermoregulate and aid digestion:
- Basking temp (arid species): 95-105°F
- Basking temp (tropical species): 85-95°F
- Use a halogen flood or basking bulb
- Position 6-12" above basking spot
- ALWAYS use with a thermostat
☀️ Outdoor tortoises
Tortoises with access to direct outdoor sunlight do NOT need artificial UVB:
- Sun through glass doesn't count — glass blocks UVB
- Outdoor time must be direct sun, not shade
- Provide shade so they can escape heat
- Outdoor time is beneficial even with indoor UVB
⏰ Photoperiod
Tortoises need consistent day/night cycles:
- Day: 12-14 hours of light (UVB + basking)
- Night: 10-12 hours of complete darkness
- No night lights — disrupt sleep
- Use a timer for consistency
📏 Placement guide
Typical indoor setup
- • UVB tube: spans 2/3 of enclosure length
- • Basking spot: directly under UVB
- • Basking bulb: over basking spot
- • Cool side: away from heat/UVB
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