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Terrarium Lighting 101

Anyone popping into this messageboard will undoubtedly see many questions
asking about lighting their terrariums so I decided that perhaps a quick
introduction to the topic might be in order for newbies to check out and get
a general idea of what is necessary to grow plants with artificial light.

It is important to use a cover over your terrarium. Whether the lid is
plastic, plexiglass or all glass with a rubber hinge in the middle it will
protect your plants from the drying heat generated by the lighting fixtures.
The lid will also keep the humidity in with the plants-where you want it. Do
not use plastic aquarium hoods that are deigned as a one piece with light
strip or screw in bulb. This is not enough light to grow plants.

Most new collectors will be using a premade fishtank converted to terrarium.
If you are using fluorescent tubes you should put AS MANY tubes over the tank
as is possible. Over a 12” wide tank (measuring from front glass to back
glass) you can easily fit 4 tubes (2 twin tub strips), over an 18” wide tank
you can fit 6 tubes, a 24” wide tank can have 8 tubes and so on (apx 2
tubes/one twin strip light per 6” of tank depth will give an intense yet
cool burning light which will make your CPs very happy).
It is also a wise idea to cover all side glass surfaces of the terrarium with
tinfoil, mylar, mirror or some other reflective material so that none of the
light is lost and it bounces around inside the terrarium infinitely. You can
tape only the top of the front flap so that you can lift it to view your
plants anytime and replace it when you're done looking so that your plants
will receive every beneficial lumen they can. The difference is immediately
obvious as one is taping the first few sheets of reflective material onto the
tank as leaves once slightly shadowed suddenly become several shades lighter
and it will be more so as new pitchers open and develop truly stunning

When your collection (or fanaticism) has grown into the stage where you
construct a large growing chamber you may need to switch to power compact
flourescents or metal halides to effectively light the entire chamber. Using
these high intensity forms of lighting and larger growing chambers will
necessitate some form of humidity and temperature control (especially for
highland Nepenthes) so everything stays in balance environmentally.

Now the Bulbs...
Artificial lighting is usually packaged with some information on the carton
detailing the qualities of the particular bulb you are about to purchase.
However, this information is useless to the hobbyist if they do not know what
it means.
Hopefully this section will help you to understand why one bulb of the same
wattage may be less suitable for your plants than another.

The Color Rating Index or “CRI” of a light bulb indicates the closeness the
bulb comes to imitating the sun. The suns CRI is 100, bulbs rated from 75-100
are suitable, 90-100 are best for simulating true “white” sunlight color.

The Kelvin rating, or “K” of a bulb determines the yellow to bluish tint of
the bulb. The suns Kelvin rating varies depending upon the latitude and
angle of the sun towards the earth.
The noonday sun in the tropical zones near the equator have a Kelvin rating
of 5000-5500K and the color is slightly “golden” (or “yellow/green”).
Whereas the noonday sun in Chicago Illinois is 6500K and is slightly “blue”
and Anchorage Alaska more towards 7100K which is even more “blue.” On the
far end of the spectrum a novelty “blacklight” is approximately
30,000-40,000K. A word of warning, using a blacklight on a CP terrarium is
essentially useless unless you wish to use it for night viewing to simulate
the moon which, by the way, is not necessary for successful cultivation but
is a fun experiment. A “soft white” or “warm white” bulb is usually around
3200K which is far too dull and yellow to be effective for photosynthesis in
the plants tissues.

Lumens is the value which should be paid most attention to when shopping for
a bulb. Lumens is a means of measuring light intensity and tells you how much
actual light will be output from the bulb. The wattage of a bulb simply tells
you how much electrical power it takes to run the bulb and is NOT a very good
indicator of how suitable the bulb is for plant growth. Usually the higher a
bulbs wattage, the higher the lumens (light output) but this is not always
so. If you compare a 40 watt screw in incandescent bulb and a 40 watt
fluorescent tube you will be getting almost 10 times the lumens from the
fluorescent tube than you will from the incandescent. Also, with expanding
technology in regards to artificial lighting such as the screw in Compact
Flourescents (often referred to as the “5 year bulb”) these put out more
light while using less electricity.
You must also remember that the further a plant is from the light the fewer
lumens will reach it and the less chances the plant will receive maximum
color spectrum (CRI) from the light the red spectrum is lost first followed
by orange, yellow green and finally blue. So while a single fluorescent Bulb
of 3200 lumens/40 watts sounds pretty good you have to remember this value
reading is taken on the bulbs surface, the number of lumens drops
considerably the farther the bulb gets from the surface, not to mention being
separated from the plants via plastic or glass on the required terrarium lid.
Thus, more bulbs are needed to be combined together help to “punch” the
light down farther to evenly illuminate all of your terrarium or growing

By far the most easily accessible form of artificial lighting for your CP
collection is the twin tube strip light. Twin tube strip lighting kits may be
purchased for as little as $5 - $20 at most home improvement centers. The
bulbs for these units are usually available in a wide range of color
temperatures to the observant buyer. Ideally a bulb color temperature of
5000-5500K and with a color rating index of 90-100 simulates tropical sun
almost exactly. GE makes such a bulb called Chroma 50 (marketed as “Sunshine”
in an orange & yellow sleeve) but they are more expensive and when using
only these bulbs one gets the feeling that the light is very “golden green”
or “yellow/green” which may be bothersome to some people. So using a bulb or
two called “cool white” or “daylight” with a color temp of 6500K-7100K to
add some blue spectrum and balance out the color to the human eye and not
affect the plants too much.

This is a relatively new form of fluorescent lighting which effectively
quadruples the output of normal flourescents in approximately 1/2 the space.
These work best for odd shaped terrariums (such as octagonal or hexagonal)
which cannot have standard fluorescent tubes placed above them due to their
unusual lengths/widths. They also work well for lighting deeper/taller
terrariums because they have 2-4 times the lumen output of standard
fluorescent tubes in a smaller bulb. A variety of lighting units, wattage's,
color temps and bulb sizes (from 6” to 47”) can be obtained from saltwater &
marine aquarium suppliers. NOTE: These bulbs cannot be used in the standard
fluorescent fixtures, a special ballast must be obtained, making their cost
more prohibitive.

These bulbs are also relatively new (often sold as “5 year bulbs”) but until
now they have been only available as “soft white” which is unsuitable as a
plant light. However several companies have begun making the screw-in bulbs
in daylight 6500K color temp which are perfectly suitable for smaller
terraria. They are available at large hardware stores from 15 watts (1100
lumens) to 65 watts (8000 lumens) in power. These are very good bulbs but
they do cost more than traditional fluorescent lighting.

These are far more advanced (and expensive) forms of lighting. Suitable
mainly to experienced hobbyists growing a large room size collection or as
supplemental lighting for greenhouses on the dark days of a gloomy northern
hemisphere winter season. Not for use on terrariums under 4' x 4' x 4.' These
forms of lighting come in wattage's ranging from 175 watts to 1000 watts. The
ballast's and bulbs both generate a great deal of heat along with the light
so temperature and humidity in an enclosed space such as a large
terrarium/grow area must be closely controlled when using these forms of
lighting so the plants are not scorched or cooked. Plants must be placed
approximately 24-36” from these types of lighting units. When using these
types of lights for a large terrraium/grow closet, etc. you will also need to
buy the following: timers, fans, humidistat and thermostat (two stage
thermostat if you are growing highlands and need to cool the room at night).
As with the Power Compacts a variety of high intensity lighting in various
wattage's and color temps may be obtained from saltwater aquarium dealers.
I should also add that when firing up a few metal halides may get you a visit
from your neighborhood DEA (Drug Enforcement Agency) due to the spike in
power usage, so long as you're just growing CPs you don't have anything to
worry about, but you should be aware of the possible knock on the door!

I hope this little article will give you some place to start when seting up a
terrraium. Light is the #1 necessity of your precious plants - please do not
skimp on it!

-Josh Cook /Swords"
So could you place compact flourecents 2-3 times higher than flourecent strip lights?
Hi Jaie,

One of the sheets that comes with the FlyTraps in the 1.5 gallon Terrarium you guys sent says "Artificial light such as soft white fluorescent lamps can be used which mimic the spectrum of light the plant enjoys."

I just got these plants like a week and a half ago and I have been using a desk lamp and a 25w compact (1750 Lumens Soft White Fluorescent) bulb brought right to the rim of the terrarium and running for about 9 hours, is this sufficient? What would you recommend for the 1.5 gallon terrarium you guys sell? I'll buy whatever bulb works best if you can recommend one....Thanks!
Nate, placing lamps farther away will defeat the purpose of using the more expensive higher output bulbs unless it is a necessity like with metal halides which can turn plants into dust if placed too close due to the heat they give off. The farther the plant is from the bulb the fewer lumens/less intensity is reaching it's target.

Lord GriNz, If you can locate the daylight spectrum screw in compact flourescents they will be far more suitable. Having screw in CF lamps that close on a small terrarium such as 1.5 gallons may cause overheating problems whereas regular flourescent tubes will give a more even light and be cooler in temp. I'd stick a thermometer in that terrarium to see what kind of temp you're getting. If you can measure the humidity as well as temp that would be the best indicator of your conditions. WalMart sells a battery operated temp/humidity gage with remote sensor for about $15 (check near their outdoor thermostats).
Hi Swords,

Sounds like it isnt going to be easy to light this terrarium, the reason I brought the tip of the bulb to about 1/2" from the rim is so the light would be more within the chamber. I dont think heat is a problem but I was wondering if 1750 Lumens was enough for that size terrarium. I mist the plants each day so they dont have a chance to dry out, they get tender loving care. Even with the soft white they are doing pretty good, but if daylight bulbs work better at what intensity(Watt and Lumen) do you recommend? the desk lamp I use has like a 4 inch like cup shaped hood that I lined with aluminum to help gather the light better. I dont want to go to nuts because they are for display even though I do want them to do well until they grow bigger and I will probably move them to a larger tank of some kind.

What I meant was, if I grow many plants satisfactory under two daylight tubes, at about 10" from the ground, could I raise a light with three times the intensity, three times the distance if I wanted to grow taller plants, and still have near equal results?
Ah, now I see what you mean!
So long as the main growing point/points of your high light loving plants are about 12" or so from the lights you should be just fine. If you place your plants too far below the lights when they are not already tall the light will not be intense enough and the plants may etoliate or stretch towards the light with large internodes between leaves and less colorful pitchers (or other traps depending upon what you're growing).
In my highland tank I have a 3 level shelf, plants which like very bright light are on the top shelf about 12" from the lights, here the leaves turn a nice red color and pitchers grow nicely. The next shelf down plants are 18" from the lights they leaves get plenty of intense light but do not turn red (the rajah did) and the 3rd shelf is 24" from the lights. Illumination on this shelf is equivelent to roughly 4 normal flourescent tubes. The 3rd shelf works good for higher light orchids, nep cuttings or just highland neps which enjoy less intense light. Beneath the shelf there is still plenty of light for growing things like ferns, lowlight orchids, aroids and what not. I also covered the back and sides of the chamber with plastic poultry wire mesh (very strong) from this I can hang net pots or mounted orchids at any level.
I would say if you don't use a shelf or hang the plants keep your lights 12" or so from the plant tops and just gradulaly move the lights up as the plants get taller.
Hope that helps!
Hi !

"...So while a single fluorescent Bulb
of 3200 lumens/40 watts sounds pretty good you have to remember this value
reading is taken on the bulbs surface, the number of lumens drops
considerably the farther the bulb gets from the surface..."

This is wrong, you are mixing lumens and lux. lux = lumen per m² and this is decreasing with more distance. The lumens are the output of the lamp and it is always the samennot depending on the place where you installed it.

Light colour between 3000 or 4000K is quite suitable for plants ! It is "warmer" than the sun, but it doesn't matter.
Even high pressure sodium works well (and this light is yellow &#33

forms of lighting come in wattage's ranging from 175 watts to 1000 watts..."

They start at 35 W in Germany !

mercury vaper is very unsuitable for carnivorous plants ! It has only around 50lumen/W and a bad spectrum.

The most advanced metal halide bulbs (HCI / CDM) have around 100 lumen / W and an excellent spectrum. They produce less heat than if you would use flouresent lights with the same lumen output !!!!!
And because of the longer ditance between bulb and plants you don't ahve to worry about overheating.
Once again : flourescent lights are heating your terrarium much more than metal halide or high pressure sodium lights !!!!! (if you compare the same power)

Hmmmm ....
I guess I am asking the question wrong....What I need to know is does anyone know how best to light the 1.5 gallon terrarium filled with VFT's that is sold on this site.

What Brand Light that will fit in a desk lamp?
How many Watts?
How many Lumens?
How far from the top of the terrarium should it be?

  • #10
hmm, well now, i'd like to shed a little "light" on this subject here, its not actually the bright beams of light itself that the plants are eating up, its the UV rays that are coming from them, the weaker the bulbs get from getting a higher position can be compinsated by just adding on a bulb and so on. my 125 gal terrarium, well, we all know how tall a 125 gallon tank is(regular one, not a high one), i started with 4 40 watt bulbs, theres a higher lvl in the back and the front wasnt getting as much light, so i made another fixture, and added 2 more bulbs in front, thats 80 more watts, oh yeah, just so you can know the output, i'll label the bulbs. 4foot, 40 watt G.E. sunshine bulbs, i havent tried any other lights yet, cept one G.E. plant & aquarium, no good, puts out more of the red spectrum. it isnt how you have to set your lights up for the plants, but for the space, think about it, there are corals in the ocean that never see daylight, but they live off of uv rays, the light isnt whats important, its the correct amount, and the right mixture of UV rays that will make them live, so, make your lighting like you would want it achieved in the middle or the top of your tank, the same at the bottom, plan from the bottom up, i learned all this from having saltwaqter reef tanks( hence, where the tank for my cp's came from, and the lighting that i made too, hehe) i was asking questions about lighting here, then i said, wait! i already know these answers! it is the intensity through out your whole tank, not just above it, i had xenia sp. mass producing like crazy from using this theory, if you have plants that need shade, buy light loving shade plants to go with em, cheaper to buy plants, then to keep messing with lighting
any comments on this? just my opinion
  • #11
I need to mention that I have now dis-assembled a lighting unit that the Flourex compact flourescent bulb comes in. It seems I was mistaken about being able to use these bulbs in a regular screw in socket, you do need the "500 watt worklight" kit to run the bulbs- because of soem extra electronics that are inside the housing however the whole lighting unit is still only $24.99. and is easily disassembled to mount in a lighting canopy.
  • #12
Hello all!

Im a new member so ill try not to appear too arrogant.
But it seems to me like some of you need to do some further research on several subjects.

"Lumens is a means of measuring light intensity and tells you how much
actual light will be output from the bulb."

Correction: Lumens is a measure of light intensity visable to the human eye. The measure of lumens is heavily weighted on the green spectrum, which happens to be the most useless portion of light for plants as they reflect green light and absorb Red and blue light.

"The wattage of a bulb simply tells
you how much electrical power it takes to run the bulb and is NOT a very good
indicator of how suitable the bulb is for plant growth."

Correction: The wattage of a bulb does tell you how much electricity it consumes and thus its output. The wattage of a bulb is the sinlge most important factor when choosing a bulb, for if no one knew what wattage bulb they were buying people would be constantly trying to modify their growing conditions to suit the variying wattages of bulbs they were buying.

I think most everyone knows you cant grow plants with an incandescent, not to mention a Mercurey Vapor! these lamps are made to light stadiums and parking lots not a greenhouse! or indoor grow room for that matter.

It must also be noted that while Power Compact Flouro's have a higher intensity they also produce a signifigantly higher amount of heat which must be dealt with.

HID or high intensity discharge is a term used for the entire group, ie. MH, (Metal Halide), HPS (High Pressure Sodium), MV(Mercury Vapor, These lights are not suitable for plant growth as they produce a color that is far too red for any plant to use alone.)

forms of lighting come in wattage's ranging from 175 watts to 1000 watts"

There are HPS and MH lamps available in wattages as low as 50 watts. And are quite suitable for small enclosed spaces.

"When using these
types of lights for a large terrraium/grow closet, etc. you will also need to
buy the following: timers, fans, humidistat and thermostat (two stage
thermostat if you are growing highlands and need to cool the room at night)"

I feel a timer is prerequisite, not to mention a fan for air movement within the environment. Humidistats and thermostats really are NOT necessities if one is observant and employs the use of a hygrometer and thermometer with min and max capabilities(these are available at Radio Shack)
If you are growing highland plants in you terrarium and you are haviing success then more power to you but to be realistic these plant really arent suitable. the conditions in most terreria are much too hot and stagnant to grow these plants succesfully.

"I should also add that when firing up a few metal halides may get you a visit
from your neighborhood DEA (Drug Enforcement Agency) due to the spike in
power usage, so long as you're just growing CPs you don't have anything to
worry about, but you should be aware of the possible knock on the door!"

This is nonsense! I have been growing with HIDs for over 10 years and not once have I ever had anyone question my power consuption. To begin most HIDs dont consume anymore than your computer! so are you saying that we should all be expecting a knock on our door? how about those of use with 2 or more computers? How about those of use that use and arc welder or 56inch HDTV or how about those of us large power tools like table saws, routing tables, jointers planers etc. etc. As you see i can got on an on ! I will tell you though that i have one friend that was contacted by local law enforcement when he first got his green house up and running in 1980!
But that is a greenhouse and represents a major draw of electrical consumption. Not a 250w, 400w, or even 1000w MH, HPS.
I hope this clears up some confusion.

  • #13
I had been looking for plans to make a light stand my dad had made for his biology class back in 1990 or so. He no longer has the plans, but I found them on the company website for the plants that were being grown in his class. These are the Fast-Grow plants used in schools to experiement with.

The light stand plans are at: http://www.fastplants.org/instructions/lighting_systems.html

I am going to build some to place over my tanks. Currently I have the tubes resting on the tops and I know this is a broken light waiting to happen.

  • #15

My wallet just exploded.

  • #16
well its worth it. one shelf for seeds and cuttings. one shelf for terrariums and another for plants. I like it so you can have the lights at different higths for different things.

  • #17
Yeah but you could make yourself the same thing for like a third the cost, a really nice one at that!

  • #18
Im thinking of getting an Envirolight for my Vft Collection

They are available in a blue or red spectrum.

Which would be more suitable for Vfts ? Someone in this review said that plants absorb both red and blue light.
  • #20
I was just wondering if it is ok to put the tubes directly onto the glass/plexiglass lid. Is there some sort of support needed to hold them off of the lid?