Terrarium Lighting Guide: UVB, LED and Full-Spectrum Explained
Three different jobs, three different bulbs — don't assume one covers all of them.
Published July 8, 2026
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"Lighting" in a terrarium actually covers three separate jobs — UVB for calcium metabolism, heat for basking and digestion, and visible/full-spectrum light for plant growth and a natural day-night cycle. A single bulb rarely does all three well, so most setups run two or three fixtures.
UVB: not about brightness
UVB lets many reptiles synthesize vitamin D3, which they need to absorb calcium properly. Without it, calcium supplementation alone often isn't enough to prevent deficiency issues in UVB-dependent species. UVB output is invisible and drops off well before a bulb visibly dims — replace on the manufacturer's stated schedule (commonly 6–12 months), not when it "looks" fine.
See UVB bulbs on Amazon →Basking heat: a gradient, not a flat temperature
Most reptiles thermoregulate by moving between a hot basking spot and a cooler zone, not by sitting at one ideal temperature all day. A single basking bulb over one end of the enclosure, checked with a thermometer at both the basking spot and the cool side, is the usual setup — an enclosure that's evenly warm everywhere removes the animal's ability to regulate its own temperature.
Full-spectrum LED for plants and visible activity
In a planted or bioactive terrarium, a full-spectrum LED strip or panel supports plant growth and gives a visible day cycle, separate from the UVB and heat fixtures. These don't replace UVB for UVB-dependent species — they cover a different part of the spectrum entirely.
Matching fixtures to enclosure size
UVB output falls off sharply with distance and mesh screening — a bulb rated for a given distance in an open-top setup may deliver much less through a mesh lid. Check the manufacturer's distance guidance against your actual enclosure height, not just the bulb's rated wattage.
UVB and heat requirements vary significantly by species — this is a general overview, not a replacement for species-specific lighting recommendations from a care sheet or vet.