Plant lights are often recommended — even required — for bioactive enclosures. Many new keepers will ask, “Why do I need a plant light? Doesn’t the UVB light already provide enough light?”
Here’s the thing: the light produced by our Sun is much more complex than it first appears. Aside from providing the visible light that marks night and day, our Sun also supplies Earth with infrared (heat) and ultraviolet energy. In keeping reptiles, we often fixate on the infrared and ultraviolet in our pets’ environment. However, in hyperfocusing on heat and UVB in our terrariums, we forget about the third, most obvious and yet overlooked factor: visible light.
Visible light has more benefits for pet reptiles than most people realize, but that’s not what we’re talking about today. Today we’re actually going to talk about plants! Plants are very important to bioactive vivariums, as we covered last month in Live Plants vs Fake Plants — Which is Better for Your Reptile?
One of the most common roadblocks that many bioactive reptile keepers face is the challenge of keeping their live plants healthy and thriving. Live plants offer many benefits to a bioactive setup, as well as to the reptile occupant. However, they can’t do much good if they’re dead or dying. And a big part of keeping your plants alive, healthy, and thriving is providing appropriate plant lighting.
Why Bioactive Vivariums Need Plant Lights
Before we dive into how to choose a plant light, let’s talk science. Why do plants need light in the first place?
Plants generally need 3 things to survive:
- Carbon dioxide
Carbon dioxide (CO2), water (H2O), and light are all essential to photosynthesis, which is the process that plants use to convert light energy into food that the plant can use, namely glucose. In photosynthesis, photons (light particles) trigger light-dependent reactions in the chloroplasts of plant cells. These chloroplasts contain a few different pigments1 which act to capture light energy for use in the light-dependent reactions of photosynthesis. These pigments are:
- Chlorophyll A: absorbs 430nm and 662nm wavelengths of light
- Chlorophyll B: absorbs 453nm and 642nm wavelengths of light
- Carotenoids: absorb 460nm and 550nm wavelengths of light
These pigments enable plants to use as much of the available light as possible. Without access to sufficient light to drive photosynthesis, plants will essentially slowly starve to death.
So Why Isn’t Your Window or UVB Enough?
UVB lights are made for reptiles, not plants. If you are using live plants with no plant light and only a UVB light, certain plants may be able to stay alive, but they will struggle to grow. More likely, the leaves will burn and the plant will slowly die. UVB bulbs aren’t very bright, which means that the plant likely won’t get enough light to fuel photosynthesis, and when starvation is combined with exposure to UV radiation, the plant’s leaves will turn brown (“burn”) and the plant will be too weak to heal itself.
If you attempt to use a nearby window as a light source for the plants in your bioactive vivarium, this will also likely not be enough for the plants’ needs. Some extremely shade-tolerant plants such as pothos may tolerate this, but most plants will require a much stronger light for them to grow. Furthermore, placing a terrarium in front of a window incurs the greenhouse effect, in which the sun’s energy heats the air inside your vivarium, where it gets trapped. This easily creates a very hot environment, which can be life threatening to your reptile.
How to Choose a Plant Light for Your Bioactive Vivarium
Because of the pigments that plants contain, it’s best to use a plant light which produces plenty of the wavelengths that they specialize in absorbing. This is why LED lights with red and blue diodes are so popular, as most of these wavelengths are in the red and blue ranges.
However, red and blue aren’t the whole story:
- 430nm = Violet
- 453nm = Indigo-blue
- 460nm = Blue
- 550nm = Yellow
- 642nm = Red-orange
- 662nm = Red
If you only provide red and blue light to your plants, then you will only be catering to some of their pigments, and photosynthesis might be hindered.
Furthermore, because you are using this light in a bioactive vivarium designed to house a reptile, you need to be aware of their light needs, too. Blue and red light will wash the enclosure in a weird purple hue, and blue light specifically is notoriously harmful to animal eyesight2.
The best way, then, to provide all of the wavelengths that your plants can use while avoiding potential harm to your pet reptile is to take a cue from nature with full-spectrum lighting. Look for a full-spectrum white plant light of 5200K to 7000K that peaks between 430-460nm and 640-670nm. 6500K to 7000K may be particularly beneficial3 for your pet reptile as well as the plants in its vivarium.
Aside from choosing the right color of light for your plants, you need to provide plenty of it. PAR stands for Photosynthetically Active Radiation, and as you may have guessed, it refers to the amount of light energy produced by a lamp that is available to plants, or between 400-700nm.
Different plants need different amounts of light. For example, some plants prefer shade, while others are categorized as “full sun” and need as much light as possible. Shade plants need a minimum of PAR 100, and full-sun plants need a minimum of PAR 700.
Finding out how much light a certain type of plant prefers is as simple as doing a Google search.
You also need to pay attention to lumens rating of the lamp in question. Lumens is a measure of the light visible by humans. The larger the lumen rating, the brighter the bulb. It is very important to not overdo it with the lumen output, as too much light can be as harmful as too little.
The general rule of plant lighting for bioactive vivariums is that the larger the terrarium, the longer, stronger light you will need. A taller terrarium, such as a 36” tall terrarium will usually require a stronger light than say, one that is only 12” tall. LED plant lights tend to be stronger than fluorescent plant lights, even the T5 HO ones.
Densely-planted or arboreal (tall) vivariums will need a plant light that spans the full length of the enclosure, and possibly more than one. More sparsely-planted vivariums may be able to get away with a shorter light fixture placed over the planted area. However, diurnal reptiles (ex: bearded dragons) in particular seem to benefit from the extra “daylight” that a plant light provides, so you may want to consider using a full-length plant light anyway.
Types of Plant Lights
The most common available plant lights on the market are LED lights and T5/T8 fluorescents.
T8 fluorescent plant lights — More energy efficient, but not as bright. Stay fairly cool to the touch.
T5 HO fluorescent plant lights — Less energy efficient, but much brighter. Fixtures tend to run warm.
LED plant lights — The most energy efficient. Brightness varies depending on number of diodes, but generally LEDs outperform fluorescents. Fixture can get hot — best to have plenty of airflow to prevent overheating.
Generally speaking, an LED grow light is going to be your best option.
The Best Plant Lights for Bioactive Vivariums
There are many different plant lights available on the current market, but here are some of my favorites:
- T5 HO fluorescent
- 2050 lumens
- 4800 lumens
- 2350 lumens
- Customizable color temperature
- Programmable 24-hour light cycle
A good plant light (especially an LED) isn’t exactly cheap. But one of the goals of a bioactive vivarium is creating a self-sustaining micro-ecosystem that will last for years, and providing enough light to adequately fuel your plants through those years is critical to your success. When your plants are healthy, your bioactive setup is more likely to be healthy. Healthy plants help circulate fresh air, aerate the soil, and form symbiotic relationships with beneficial microfauna. And fortunately, plant lights have long lifespans.
Installing a plant light over your bioactive vivarium will also likely contribute to the health and wellbeing of your pet reptile, as it helps create a more realistic spectrum of light in the enclosure, better re-creating sunlight and enabling your reptile to see in full color. Furthermore, using a plant light can help create a better photoperiod (day length), which has been noted to be important to the preventing disease and reproductive failure in reptiles4.
Will the plant light bother nocturnal and crepuscular reptiles? Most likely not. These reptiles may have extra-sensitive eyes to help them see at night, but keep in mind that they also tolerate real sunlight in the wild — and real sunlight is typically much brighter than what we are able to create indoors. As long as your reptile has plenty of options for shade and hiding places to sleep in during the day, they will not be bothered by your plant light.
And, of course, a good plant light will make your bioactive setup look extra beautiful — perfect for illuminating Instagram photos, too!
Bottom line: Plant lights are essential to successful bioactive vivariums, and they are an investment very much worth making.
About the author: Since the age of 13, Josh Halter has had a passion for making his pets’ enclosures emulate their natural habitat as closely as possible. Decades later, this passion evolved into The Bio Dude. With a retail location in Houston, TX, USA, and shipping all over the country, this store makes planning and building beautiful, functional bioactive enclosures easy for anyone who wants to give it a try.
This article was edited by Mariah Healey.
1. Pigments. (n.d.). Retrieved July 07, 2020, from https://www2.mcdaniel.edu/Biology/botf99/photo/p3igments.html
2. Tosini, G., Ferguson, I., & Tsubota, K. (2016, January 24). Effects of blue light on the circadian system and eye physiology. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734149/
3. Courteney-Smith, J. (2018). Qualities of Light and How They Are Measured. In Fire: The sun, its use and replication within reptile keeping (p. 66-69). Cambridge, UK: Monkfield Nutrition.
4. Mader, D. R. (2006). General Husbandry and Management. In Reptile Medicine and Surgery (2nd ed., p. 30). St. Louis, Missouri: Saunders.
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