Quick answer: For most planted terrariums and vivariums, use a quality full-spectrum LED rated around 6,000–6,500K, mounted on or above the screen top, on a timer for 10–12 hours a day. Brighter is usually better for plants as long as you manage heat. For reptiles, plant lighting is added on top of the UVB and basking heat your animal needs. It never replaces them.
Why light matters more than anything else
Plants make all their energy from light. In a terrarium, the light you provide is the only light they get, because room light and windows contribute surprisingly little through glass and screens. Most "mystery" plant problems come down to light: stretching stems, fading colour, moss browning in the bottom third of the tank, bromeliads turning green, succulents leaning. Fix the lighting first and many other issues disappear.
Key terms in plain language
| Term | What it means | Why it matters |
|---|---|---|
| Kelvin (K) | The colour of white light. ~3,000K is warm yellow; 6,500K is daylight white; 10,000K+ is cool blue | 6,000–6,500K looks natural and supports plant growth well |
| Lumens | Brightness as seen by the human eye | A rough guide only; plants "see" light differently |
| PAR | Photosynthetically Active Radiation, the 400–700 nm light plants use | The concept that matters for growth |
| PPFD | How much PAR reaches a spot, in µmol/m²/s | The actual measure of "how much light" a plant gets at a given depth |
| Photoperiod | How many hours lights are on per day | Consistency matters; 10–12 hours suits most tropical plants |
| CRI | Colour Rendering Index, how true colours look | High CRI makes plants and animals look natural |
How much light do terrarium plants need?
Light intensity drops quickly with distance and passes through screens poorly. Fine mesh screen can block a significant share of light. Plants near the top of a tall vivarium can get several times more light than plants on the floor. As a general guide:
- Low light (ferns, fittonia, many mosses, Marcgravia): bottom and middle of a well-lit enclosure.
- Medium light (pothos, philodendron, peperomia, begonias, most bromeliads): middle and upper areas.
- High light (colourful Neoregelia, Tillandsia, succulents, orchids that flower): top third, close to the fixture.
Place plants by light needs. See our guides to bromeliads, orchids and moss for specifics.
Choosing an LED
- Use a dedicated terrarium or plant LED, not a single household bulb. Bar-style LEDs spread light evenly across the whole enclosure.
- Look for 6,000–6,500K full-spectrum white light. Purple "blurple" grow lights work for plants but make your enclosure look unnatural.
- Match the length of the light to the enclosure. A 45 cm wide enclosure needs a fixture covering most of that width.
- Use two fixtures for tall enclosures (60 cm+), or for builds full of high-light plants.
- Mount above, not inside. Most terrarium LEDs sit on the screen. Some keepers mount them on glass tops for less light loss, but watch the heat and humidity.
Photoperiod and timers
Plants and animals both benefit from a consistent day length. Run lights 10–12 hours a day on a timer. Some keepers vary the photoperiod seasonally. Shorter days in winter (e.g. 10 hours) and longer in summer (12–13 hours) can encourage breeding in frogs and flowering in some orchids. A cheap plug-in timer is one of the best investments you can make for a planted enclosure.
Lighting plants alongside reptiles
Reptile enclosures often need three different light sources, each with its own job:
| Light | Purpose | Notes |
|---|---|---|
| UVB (T5 HO linear tube) | Vitamin D3 synthesis, health and behaviour | Essential for most diurnal reptiles; follow species-specific guidance on UV levels |
| Basking / heat lamp | Creates a temperature gradient | Keep plants well away from the hot spot |
| Plant LED | Brightness and plant growth | Adds visible light so the whole enclosure is bright and natural |
UVB bulbs alone aren't enough for most plants, and plant LEDs don't provide UVB for reptiles. In desert builds, strong UVB and bright LEDs together help succulents stay compact and colourful. See our desert plants guide.
Managing heat from lights
Modern LEDs run far cooler than old fluorescents or halogens, but a powerful LED on a glass top can still warm a small enclosure in summer. Canadian homes swing a lot: dry, cool winters and humid summers that can push indoor rooms past 28°C. Monitor temperatures with a digital thermometer at plant height, especially for cool-growing orchids and dart frogs, which can be stressed above roughly 27–28°C.
Signs your lighting is wrong
| Sign | Too little light | Too much light / heat |
|---|---|---|
| Growth habit | Long gaps between leaves, leaning toward light | Compact, but leaves crisping or curling |
| Colour | Fading, variegation lost, bromeliads turning green | Bleached, yellowing or reddish leaves |
| Moss | Thinning, yellow in lower areas | White, dry patches near the light |
| Algae | Rare | Can increase on glass and wet surfaces |
FAQ
Can I use a regular LED bulb for terrarium plants?
A household daylight bulb is better than nothing, but it usually lights only one spot. A bar LED made for terrariums or aquariums spreads light evenly.
Should terrarium lights be on 24/7?
No. Plants and animals need darkness. Continuous light stresses animals and doesn't help plants.
Does light colour affect moss?
Moss grows well under standard 6,500K white light. Brightness and moisture matter far more than exact colour.