AQUARIUM LIGHTING INTENSITY AND QUALITY IN THE HOME AQUARIUM

  Aquarium Lighting Intensity and Quality Overview
 
Aquarium lighting does far more than just illuminate the aquarium itself, proper aquarium lighting can greatly enhance the appearance of fish, plants, corals and invertebrates along with providing vital health benefits to all types of aquarium life forms. Thus, there are many important factors to consider when selecting the correct lighting system for your aquarium. When choosing the correct aquarium lighting system for a particular aquarium setup, the hobbyist needs to their best to replicate the natural lighting conditions that their aquarium inhabitants would experience in nature. Fortunately with the recent advancements in aquarium lighting systems, this has become much easier to do due to the introduction of complex lighting systems that simulate all types of natural lighting environments even night time lighting as well. In order to put together the best lighting for a particular aquariums needs, it is important to know the factors that go into deciding on which lighting system to choose.
 
The main factors involved in choosing the correct aquarium lighting system are the lighting spectral qualities and lighting intensity. There are many factors the affect the lighting quality and intensity of a lighting system, thus the following factors: water depth, water clarity, water movement and lighting intensity should be taken into consideration before making a lighting system decision. Understanding the natural conditions of your aquarium inhabitants and their lighting needs along with understanding your home aquarium environment are critical to implementing the best lighting solution for your aquariums needs.
 

 
  Lighting Spectral Qualities
 
Lighting Spectrum is something most aquarium hobbyists have heard about in connection with aquarium lighting, but probably do not have a full understanding about exactly what it is and what it means for their aquarium inhabitants. Sunlight is a combination of many types of light blended together, with the red, yellow and green areas of the spectrum being the ones most easily visible to the human eye. Ultraviolet, in the blue end of the spectrum, is invisible but its effect can be felt very easily as it is this end of the spectrum that causes the warm sun sensation you feel on your skin from the sun and causes sunburn when overexposure occurs. You can usually feel a quick change in temperature of your skin when a cloud passes over, this signals a decrease in the amount of radiation in a given light field. For humans prolonged exposure to this type of light is dangerous to both our skin and eyes; however, in the aquarium environment this UV radiation plays an important role in coral, plant & invertebrate health and photosynthesis.
 
The spectrum of bulbs for aquariums are expressed as a color temperature given or stated in Kelvin degrees. Sunlight has a color temperature of about 5500K, at 12 noon over a tropical reef while actinic light sources typically have a color temperature of about 7100K. The more blue the light the higher the temperature. Light is electromagnetic energy in the form of waves, with these waves having frequencies. As the temperature of a substance increases, the frequency of the light emitted also increases, thus lower temperatures produce red and yellow light, while higher temperatures produce light ranging from white to the blue colors of the spectrum.
 

 
In nature, as light enters and passes through the first 15 feet of water, the red and orange wavelengths are absorbed by the water, increasing the Kelvin rating of the light, and giving the light a more blue appearance. As the light penetrates to 30 feet, the water absorbs the yellow spectrum, and when the light continues past 50 feet, the water filters the green wavelengths, leaving just the blue and violet wavelengths resulting in the light with the highest Kelvin rating. This is not so noticeable in the home aquarium as we typically do not maintain aquariums with a depth of 15 or more feet!
 
Poor quality lighting products not intended for the aquarium hobby typically have Kelvin ratings in the 2700k to 4300K range which produces too much red and yellow light. These lighting products are not only undesirable because they do not provide the needed lighting qualities for most aquarium plants and corals, but they also promote undesirable types of nuisance algae. While the quality of aquarium lighting and its affects on aquarium inhabitants is extremely important, so is the look or aesthetics of the aquarium as well. It is important to select bulb types and spectral qualities that satisfy both the needs of your aquariums inhabitants and also provides a pleasing aesthetic for the aquarium hobbyist as well.
 
  Lighting Intensity
 
Lighting intensity is measured as Lux at the surface it impacts and as watts when measured at its source. Since light spreads outward and scatters in all directions, the farther we are from the source the less light we see. The intensity of light decreases by the square of the distance that area is from the lighting source. If a fluorescent bulb is moved 2 inches away from the water, it will be 4 times lower in intensity. This is an important fact to remember when placing bulbs that appear at first to have the correct amount of intensity for an aquaria. As you raise them higher above the water, the intensity will drop dramatically and you might not have the correct amount of light reaching your animals.
 

 
Lighting intensity can be affected by other factors other than distance. Turbidity of the water can significantly reduce the actual amount of light that penetrates the surface and reaches the animals. In tanks where activated carbon is used and is changed regularly light penetration into the aquarium can be maximized. Cleaning or removing glass or acrylic lenses from the light hood will also help. The intensity of light above the surface of a reef can be as high as 130,000 lux. The actual amount of intensity that penetrates the surface of the water can be about 70,000, with maybe only 15,000 lux actually reaching the 10-15 meter mark. The water surface also reflects some of the light back, reducing the amount that penetrates the water and reaches the corals.
 
Light intensity at the source is measured in watts. The higher the watts, the more intense the light, and the more energy required to produce the light. A 100-watt bulb, for example, will give off more light than a 40-watt bulb, and will cost more to use. A watt is actually related to a lux in that one lux is equal to 1.46 milliwatts (0.00146 watts) of energy of one specific frequency (555 nm) hitting a surface area of one square meter. However, since bulbs used in aquarium lighting systems emit light of many frequencies (not just 555nm), no exact formula can be used when determining the number of lux produced by a bulb of a specific wattage.
 

 
It is also very important to note that some types of aquarium light bulbs (metal halide, fluorescent, etc.) begin losing intensity long before they stop emitting light. The general rule of thumb is to replace these type of aquarium bulbs every 8 to 12 months with some reef aquarium lighting needing replacement every 6 months. These times will vary based on bulb type and lighting requirements for a particular aquarium, so one should consult the documentation for the bulb type being used.
 
In nature most corals and marine invertebrates live in conditions that are lit mostly by blue light waves, thus they have adapted to this and will require bulbs that produce these blue wavelengths in the aquarium environment as well. While corals and marine invertebrates thrive under blue light, most hobbyists find aquariums illuminated with blue light only to be unattractive. This aesthetic dilemma can be solved by combining an actinic light with a white light, such as a 50/50 bulb half blue/white or a light combination in which the white lights give light in the range of 8000 to 12000 K. This lighting combination gives corals and invertebrates the spectrum necessary for growth, in addition to the spectrum necessary for accurate color rendering within the aquarium.
 

 
Lastly, it is important to consider initial and ongoing operating costs, lighting intensity and spectrum and the heat produced by the lighting system when choosing a lighting system for your marine reef aquarium. Lighting systems for reef aquariums, such as metal halide and hi-output fluorescent systems, tend to be rather expensive due to their high initial cost, high levels of required energy, and characteristically frequent bulb changes.
 
Lighting systems designed for reef aquariums produce two types of intense heat, which must be addressed prior to installation. The first type of heat - from the actual bulbs - surrounds the bulbs and should be removed with cooling fans. The second type of heat - radiant heat produced by the lighting system - is unavoidably absorbed by the aquarium water and should be controlled with a water chiller (be sure to budget for a water chiller in your installation plans). Fortunately a large number of LED aquarium lighting systems for both freshwater and marine environments are becoming widely available and at a variety of cost points. These newer LED lighting systems require much less energy, produce less heat, long bulb life and produce full spectrum quality light even towards the end of the bulbs life span.
 
  In conclusion
 
When choosing lighting for your aquarium, keep your aquarium inhabitants natural lighting conditions foremost in your mind, while still budgeting for the initial cost of the lighting system and for replacement bulbs. Other factors such as heat produced from the lighting system, physical size and dimensions of the system and airflow should also be considered before purchasing a lighting system. Having the correct wattage, Kelvin rating and lighting intensity can mean the difference between an aquarium with beautifully colored fish, thriving plants and corals and a tank overgrown with nuisance algae.