Lighting is where most terrariums and vivariums quietly fail. The plants survive but stay leggy. The reptile grows but develops slight calcium deficiency. The keeper assumes the build is fine because nothing died, but it is operating below its potential. Picking the right lighting is not complicated, but it does require understanding what wavelengths plants and animals actually need, and how those needs change based on inhabitant and enclosure depth. This guide covers UV, LED, and grow lights in practical terms so you can buy once and skip the upgrade churn.
What plants need from light
Plants use light for photosynthesis. Two metrics matter.
PAR (Photosynthetically Active Radiation) measures the photons in the 400 to 700 nm range that drive photosynthesis. Different plants need different PAR levels at substrate or canopy height.
- Low-light plants (java fern, anubias, most mosses, fittonia, peperomia): 15 to 40 PAR.
- Medium-light plants (most tropical understory species, bromeliads, ferns): 40 to 80 PAR.
- High-light plants (carpet plants in aquariums, demanding stem plants): 80 to 150 PAR or more.
Color spectrum matters less than total PAR for most terrarium plants, but a full-spectrum light (with blue 450 nm and red 660 nm peaks plus white fill) supports the broadest range of species.
A common rule of thumb: a grow LED rated 30 to 40 watts placed 10 to 14 inches above the canopy will grow most tropical plants in a 60 to 110 liter enclosure.
What animals need from light
Animal lighting needs split into three bands.
Visible light: any reasonable LED that lets the animal see by day. Nocturnal species need a normal day-night cycle, not high brightness.
UVA (320 to 400 nm): supports normal behavior, appetite, breeding, and feeding response. Most reptiles benefit. Amphibians generally do not require it.
UVB (290 to 320 nm): required for vitamin D3 synthesis, which is required for calcium metabolism. Without it, diurnal reptiles develop metabolic bone disease over months to years. Critical for bearded dragons, leopard geckos (more debated, increasingly recommended), uromastyx, day geckos, anoles, monitors, and basking turtles.
UVB is not optional for the species that need it. A diurnal reptile in a UVB-free enclosure will eventually develop calcium issues even with calcium-dusted feeders and vitamin supplementation. The supplement route does not fully substitute for UVB.
Which animals need UVB
UVB required:
- Bearded dragons.
- Uromastyx.
- Diurnal day geckos.
- Anoles (green, brown).
- Basking turtles (red-eared sliders, painted turtles).
- Most diurnal lizards.
UVB recommended or debated:
- Leopard geckos (older guidance said no, current 2026 consensus says low-output UVB is beneficial).
- African fat-tailed geckos.
- Crested geckos (older guidance said no, current consensus says low UVB is beneficial).
UVB not needed:
- Most amphibians (dart frogs, fire-bellied toads, salamanders).
- Mourning geckos (debated, low-output UVB is increasingly recommended).
- Pure nocturnal species kept indoors without basking opportunity.
When in doubt, low-output UVB (Arcadia ShadeDweller, Zoo Med 2.0) is the safer addition rather than the omission.
UVB bulb types
Three options dominate the market in 2026.
Linear T5 UVB tubes:
- Highest UVB output and best spectrum.
- 12 to 18 month lifespan.
- Standard for bearded dragons, uromastyx, monitors.
- Brand examples: Arcadia ProT5, Zoo Med Reptisun T5 HO.
Compact UVB bulbs (CFL-style):
- Lower output, narrower coverage area.
- 6 to 9 month lifespan.
- Suit small enclosures and species with lower UVB needs.
- Brand examples: Zoo Med Reptisun 5.0, Exo Terra Repti-Glo 10.0.
Mercury vapor UVB:
- Combines heat and UVB in one bulb.
- 12 to 18 month lifespan.
- Higher power draw and significant heat output.
- Best for large enclosures with high heat needs.
- Brand examples: Solar Glo, Powersun.
UVB output degrades long before the bulb visibly burns out. Many bulbs lose 50 to 80 percent of their UVB output within their rated lifespan. Replace on schedule, not on visual appearance.
LED grow lights for plants
LED grow lights have largely replaced T5 fluorescents and metal halide for terrariums in 2026. Three approaches:
Full-spectrum white LED panels:
- Most natural-looking light.
- 4000 to 6500K color temperature.
- Common brands: Sansi, Mars Hydro, Aquario.
- Suit display vivariums and plant terrariums.
Red and blue diode panels:
- Higher efficiency for plant growth.
- Magenta-tinted light, less pleasant to the eye.
- Best for closed grow setups, not display enclosures.
Hybrid panels with white plus red and blue diodes:
- Best of both worlds.
- Natural color rendering with extra growth-driving wavelengths.
- Common in higher-end terrarium fixtures.
For a 60 to 110 liter planted vivarium, a 30 to 50 watt full-spectrum LED panel covers most plant needs. Larger or taller builds need 50 to 100 watts.
Photoperiod and timing
A timer is mandatory. Manual on-off causes stress for animals and uneven growth in plants.
Standard photoperiods:
- Tropical terrarium with no animal: 8 to 10 hours.
- Tropical vivarium with diurnal reptile: 10 to 12 hours.
- Adjusted for seasonal mimicry: 8 hours in winter, 12 hours in summer.
Ramp timers that gradually brighten and dim the light reduce stress for diurnal species. Many modern terrarium fixtures include built-in ramp functions.
UVB photoperiod usually matches the plant or visible light photoperiod. Some keepers run UVB for fewer hours than visible light. The animal still gets a full day cycle but a shorter UVB window.
Heat and lighting overlap
Lighting and heat overlap because most heat sources emit visible or UV light.
- Basking spot bulbs (incandescent or halogen): visible light plus heat.
- Ceramic heat emitters (CHE): heat only, no light, useful for night.
- Mercury vapor: heat, UVA, UVB, and visible light combined.
- Deep heat projectors: infrared-A heat with no visible light.
For diurnal reptiles, the basking spot must be lit during the day. For nocturnal species or supplemental nighttime heat, ceramic or deep heat projectors avoid disturbing the dark cycle.
Common lighting mistakes
- Skipping UVB on a species that needs it. The damage is gradual and irreversible.
- Mounting UVB through glass or acrylic. Glass blocks 95 percent of UVB. Use mesh screen tops or open-top fixtures only.
- Placing UVB too far from the basking spot. Output drops sharply with distance. Most fixtures need to be within 10 to 14 inches of the animal.
- Never replacing UVB bulbs. The bulb still looks fine at 18 months. The UVB output is functionally zero.
- Running grow lights too long. 14 to 16 hour photoperiods stress plants and disrupt animal cycles. Stick to 10 to 12 hours.
Good lighting is set-and-forget once it is correct. Spend an hour up front matching the fixture to the inhabitant, mount it at the right distance, set the timer, and replace UVB bulbs on schedule. Plants will fill in, animals will stay healthy, and the build will look the way you imagined when you started.
Frequently asked questions
Do all terrariums need UV lighting?+
No. Plant-only terrariums do not need UV. Most amphibians (dart frogs, fire-bellied toads, salamanders) do not require UVB. Reptiles like crested geckos, leopard geckos, and bearded dragons benefit from or require UVB. Decide based on the inhabitant.
UVA vs UVB: what is the difference for reptiles?+
UVA (320 to 400 nm) supports normal behavior, appetite, and breeding. UVB (290 to 320 nm) is required for vitamin D3 synthesis and calcium metabolism. Diurnal reptiles like bearded dragons need both. Nocturnal species often manage on UVA alone.
How long should lights be on each day?+
8 to 12 hours daily is the standard for both plants and most reptiles. Diurnal reptiles align with a normal day length (10 to 12 hours summer, 8 to 10 hours winter). Plants tolerate longer photoperiods but show stress at over 14 hours without darkness.
Will a regular LED bulb grow terrarium plants?+
A regular warm-white LED bulb will keep low-light plants alive but most terrarium plants need a dedicated grow light or full-spectrum LED rated for plant growth. Look for 4000 to 6500K color temperature and a PAR rating above 30 at substrate level.
How often should I replace UVB bulbs?+
Linear T5 UVB bulbs typically last 12 months. Compact UVB bulbs last 6 to 9 months. Mercury vapor bulbs last 12 to 18 months. UVB output degrades long before the bulb visibly burns out, so mark the install date on the bulb itself and replace on schedule.
