Doyle's Dart Den
by David Doyle
Light serves three purposes in your vivarium:
· Allow you to view your box of nature
· Allow the animals to see so they can function
· Allow the plants to grow
The following paragraphs provide the information to allow you to select a lighting system that best suits the needs of you and your vivarium.
Us and the Light
Here the purpose is to provide a light source that will allow us to view our creation and in the end isn’t that what we are working for. Just about any light will server this purpose but there are things we should consider to allow us the best viewing. Light is electromagnetic energy (radiation) just like X-rays or radio waves. This radiation travels in waves just like the waves in water. There is a crest and trough. The wavelength is the distance between 2 crest or troughs. Some electromagnet radiation has very short wave lengths such as x-rays, which has a wavelength of around 1 nanometer (nm) (1x10-7 cm) which means that over 25 million waves would fit into one inch. Some electromagnet radiation has very long wavelengths such as AM radio, which has a wavelength of 1-100 meters. Visible light is the radiation that ranges from 380 nm to 770 nm. Alex Ryer Light Measurement Handbook, 1997, ISBN 0-9658356-9-3 p. 157. [online] Available at: www.intl-light.com/handbook/ The shorter wavelengths appear blue and the longer wavelengths appear red. All of the other colors fall in-between these or are combinations of colors. When we see color we see the light an object is reflecting. Some objects reflect all of the wavelengths and therefore appear to be white. Other reflects no light and appear black. An object that appears to be blue is adsorbing all of the colors but the blue portion (spectrum) of the light.
Wavelength is just one of the parameters of light source. Some of the others parameters are:
The spectrum of a light is the distribution of the wavelengths that a light source emits. As discussed above visible light ranges from 380 to 770 nm. The human eye responds best to light in the yellow-green range (555 nm) of the spectrum and decreases as the wavelength is shortened towards the blue range or lengthened towards the red range.
Plants respond just the opposite. Greater on the blue and red sections and less at the green section with 2 peaks in the spectrum they respond the best to. This makes sense when one thinks about plants appear green which means they are absorbing all the colors but green which is what they are reflecting. The larger of the 2 peaks is between 400 and 475 nm with the peak at 450 nm. The second and slightly smaller peak is in the red range between 630 and 675 nm with the peak at 675 nm. M.J. Farabee (2000) Photosynthesis [On-line] Available at: http://gened.emc.maricopa.edu/bio/bio181/biobk/biobookPS.html
Color Rendering Index (CRI)
Have you ever noticed how someone’s hair color or the color of clothes seems to change form inside to outside? This is normally because of the CRI of the lights inside is low and does not compared to natural sunlight. The CRI is a measurement of how close a light source compares to natural sunlight to the human eye. Sun light has a CRI of 100. A light source with a CRI of 80 to 100 is considered to be good. For the human eye viewing pleasure of our vivariums we should try to have light sources that have an 80 or higher CRI.
As a piece of metal is heated with a blowtorch it first glows dull red then bright red and then at the hottest temperatures it will glow bluish white. Color temperature describes the color of light by the same method. Color temperature is defined as the temperature that a perfect electromagnetic radiator “black body" emits at a given temperature. The temperature scale used is degree Kelvin (to convert Celsius to Kelvin add 273° to the temperature Celsius) The tricky part is the lower the color temperature (redder the color) the light is described as “warm”; the higher the color temperature (bluer the color) the light is described as cooler. The following are some common light sources and their color temperature. Charles Delbeek and Julian Sprung The Reef Aquarium, 1994, p. 187 ISBN 1-883693-12-8
For the human eye viewing pleasure of our vivariums most people use 5000°K to 7500°K light sources.
A watt is defined by Merrian-Webster's Collegiate Dictionary as:
The absolute meter-kilogram-second unit of power equal to the work done at the rate of one joule per second or to the power produced by a current of one ampere across a potential difference of one volt, 1/746 (0.134 %) horsepower
This is the amount of electricity used by the lamp over the course of one hour. It can be used as a general measurement of the brightness of the lamp. For example a 15-watt bulb consumes less electricity than a 30-watt bulb and also produces less light.
This is the number of hours it is expected that the bulb will last while on. Much like the average life experency of humans it is an average. If a bulb is rated for 10,000 hours the bulb may last 5,000 or 20,000 hours.
Lumens is defined by Merrian-Webster's Collegiate Dictionary as:
A unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of one candle intensity
A lumens can also be expressed by 683 lm = 1 watt at 555 nm or 1 lm = 0.001464 watt at 555nm (do not confuse a watt of energy emitted by the lamp and the amount of watts used by the lamp.) Alex Ryer Light Measurement Handbook, 1997, ISBN 0-9658356-9-3 p. 30. [online] Available at: www.intl-light.com/handbook/
Ok that still really doesn’t tell you what lumens is but just think it as a general measurement of the amount of light produced.
Photosynthesis photon flux density (PPF or PPFD)
This is a measurement of the number of light quantum (photon) in the range of 400 - 700 nm strike and an area in a given amount of time so the units are Number / Area / Time. The greater this number the greater the potential for photosynthesis. The unit is micromole photons/m2/second (umol m-2s-1). One mole equals 6.02 x 1023. Hoshi, Takehiko, Ph.D, The Unit Concerning the Light in the Plant Production
1999, [Online] available at: http://www.fb.u-tokai.ac.jp/WWW/hoshi/env/light.html and Personal communication with Brent Block via The Vivarium email group Tuesday, March 06, 2001 8:31 PM. This is the most useful information regarding a light source but the hardest to obtain.
There is much debate regarding the quality of light required for animals. Certain reptiles require UV light to produce vitamin A and D. Vitamin D is required for the animals to utilize the calcium in their diets. UV light is divided into 3 ranges:
Alex Ryer Light Measurement Handbook, 1997, ISBN 0-9658356-9-3 p. 6. [online] Available at: www.intl-light.com/handbook/
The case for amphibians needs for special lighting is not as clear. I seen several breeders that use normal fluorescent lamps with successful results but again our goal is to create an environment that is optimum for the animals. Vivaria Projects reports that they had conducted an experiment where they made 2 groups of 10 Epidobates tricolors in each group and place one group in an vivarium with lamps that emitted UV light and the other group in a vivarium with normal lights. After 3 months the group the group with the UV light appeared redder. They also reported that a group of Phyllobates vittatus that had suffered seizures were exposed for UV light for two months and most did not suffer seizures after the exposure. Also a seven-year-old, green Dendrobates pumillio which had changed to a brown color returned to its green color after three peelings. Their article can be seen atand their main page can be found at . There is also some evidence that Homo sapiens (that would be us) can suffer depression if they are not exposed to full spectrum light. This is known as " Seasonal Affective Disorder (SAD)". With this information, there is evidence that full spectrum is beneficial for the animals.
We all learned in elementary school that plants through the process of photosynthesis convert electromagnetic energy (light) into chemical energy. Merrian-Webster's Collegiate Dictionary defines photosynthesis as:
of chemical compounds with the aid of radiant energy and especially light;
especially: formation of carbohydrates from carbon dioxide and a source of
hydrogen (as water) in the chlorophyll-containing tissues of plants exposed to
6CO2 + 6H2O + light energy = C6H12O6 + 6O2
M.J. Farabee (2000) Photosynthesis [On-line] Available at:
The water can be found in our vivarium and the carbon dioxide is provided by the atmosphere which has 0.03 -0.04% carbon dioxide and the animals in the vivarium which convert their food into energy and carbon dioxide (the reversal of photosynthesis) through the process known as aerobic respiration. With this in mind we must provide adequate quantity and quality of light for the plants to thrive.
In the rain forest, the animals and plants have the best source of light available - the Sun. The goal in the vivarium is to recreate nature as much as possible. When determining which lighting system to use, consider the following:
Natural Sunlight provides all of the best but is hard to control. Normally the light will be entering the building through a window and normally the back of the vivarium is to the window. To use natural sunlight in this manor, no background can be used and the vivarium is backlite. Backlighting cause the side of the vivarium that is viewed to be in shadow and lessens the aesthetically pleasing. If the room is a sunroom or has a skylight this problem can be avoided. Sunlight can raise the temperature of the vivarium. Also each time the light passes through a "Transparent" material the amount of light is reduced. The following table was generated by Melissa Kaplan and shows the amount of UV A and B that remains after passing through various materials.
Standard Incandescent Lights
Standard Incandescent lights are the light bulbs that you screw into the socket and are the most commonly available type of lights. They produce light by using electricity to heat a wire filament, which glows. The benefits are they are cheap and readily available. The disadvantages are they produce a large amount of heat, low color temps. and use a large amount of energy for the amount of light produce. (This is because a large amount of the energy is emitted as heat.) The color temperature is approximately 2,700 º K and the CRI is 100.
Halogen lights work off the same principle as standard incandescent lights. A tungsten filament is heated by electricity passing through the filament and then the filament gives off light. In standard incandescent lamps the problem is that the tungsten filament evaporates over time and a layer of tungsten is deposited on the glass of the lamp. In halogen lamps, one of the halogen gasses, Iodine or Bromine, is placed inside of the lamp. When the lamp reaches at least 392º F (200º C) the "Halogen Cycle" takes place I the lamp. The cycle is:
This results in the filament lasting longer and the production of more light. The color temperature is approximately 3,000º K and the CRI is 100
Fluorescent lamps generate light by having an anode at one end of the tube and a cathode at the other end of the tube. Note: in an electron tube the anode is the electron-collecting electrode and the cathode is the electron-emitting electrode. (Merrian-Webster's Collegiate Dictionary, [Online] http://www.m-w.com) The inside of the tube is a partial vacuum approximately 1/1,000 th of an atmosphere (this is why fluorescent tubes make a boom when cracked) filled with mercury vapor (Louis A. Bloomfield, How Things Work - Fluorescent Lamps, [Online] http://rabi.phys.virginia.edu/HTW//fluorescent_lamps.html). As current is passed across the anode and cathode the cathode generates electrons which are sent to the anode. As the current passes though the mercury vapor, the mercury vapor is ionized and emits ultraviolet radiation mostly in the 254-nanometer wave length (Louis A. Bloomfield, How Things Work - Fluorescent Lamps, [Online] http://rabi.phys.virginia.edu/HTW//fluorescent_lamps.html). The ultraviolet radiation then excites the electrons of the phosphor powder that lines the inside of the tube and this emits light. The characteristics of the light are controlled by the type of phosphor powder in the tube.
So the question comes up "What is the ballast for?". The ballast acts as a transformer to regulate the voltage and limits the current allowed to enter the lamp. Without ballast the current would increase to a point that the tube would explored. The things to keep in mind regarding ballast are:
For more information about ballast see:
Advance Transformer Co - Purpose of a Ballast - Very detail information.
Why replace the tubes every 6 months? During the process above the cathode slowly is degraded and deposited on the inside of the tube. Over time this will cause a reduction in the amount of light generated and shifts in the characteristics of the lights. For vivariums, I don't think every 6 months is necessary but it is a good ideal to change them every 12 to 18 months.
Money Saving Hint: If you have friends that keep saltwater reef tanks, ask them for their lamps when they change them. They still will give you good light for quite a bit of time.
Compact fluorescent lamps work on the same principle as standard fluorescent lamps but they are more “compact” and therefore more light can be placed over the tank. Many people that use these report good results. One should keep in mind these lamps produce more heat than standard lamp. Also the initial cost is greater than Standard Fluorescent Lamps.
High Output and Very High Output Fluorescent
These lamps also work on the same principle as standard fluorescent but operate at higher current and therefore produce more light. These lamps have become less popular with the introduction of the Compact fluorescent. As with the Compact Fluorescent Lamps they produce more heat and have high initial cost.
High Intensity Discharge Lamps (Mercury vapor, Sodium vapor and Metal halide)
High Intensity Discharge Lamp (HID) have a small inter bulb contains the vapor which an arc is passed through. This is incased in an larger bulb. Mercury and sodium vapor bulbs are common sold in hardware stores. Sodium vapor bulbs typically do not produce suitable spectrum. Metal halide and to some degree Mercury vapor are used for salt reef tanks. The main disadvantage to HID lamps is the cost and the amount of heat they produce. The Marine Aquarium Reference System and Invertebrates by Martin Moe 1993 states that the lamp should be suspended 1.5 to 3 feet above the tank because of the heat. and but the light is yellowish