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Aquarium Lighting


The Importance of Lighting

aquarium lights

Most novice aquarists underestimate the importance of lighting on their new fish environments. The average aquarium set-up contains one all-purpose bulb which implies that special lighting is not necessary.

Lighting is of VITAL importance to the marine aquarist and a high priority for tropical fish keepers if they wish to simulate a true under-water environment that is both healthy and visually appealing.

Corals and invertebrates use lighting to regulate and assist in digestion, feeding, reproduction and growth. Plant aquariums need proper lighting in order for plants to thrive. A fish-only tank will benefit from correct lighting with increased coloration, activity and spawning.

Light Spectrum

light spectrum

The most obvious use of lights is to light the tank so that you can see your fish. Light spectrum runs from violet on the short end (320 nanometers) to red on the long end (700 nanometers). Remember your red, orange, yellow, green, blue, indigo, violet light spectrum? Below are two light bulb spectrums represented visually by peaks and valleys on a ROY G BIV scale.

The sun has 3 wavelengths: UVA, UVB, and UVC. UVA is the visible wavelength of light and is responsible for the "physiological well being" of fish. The 420nm blue (UVA) range is particularly important to marine corals and invertebrates and also helps stimulate feeding and breeding behavior in fish.

UVB is the non-visible wavelength of lighting. UVB is the spectrum which gives humans a suntan. This is a critical component for reptiles in that the 320nm range of violet (UVB) is needed for many animals to assimilate calcium into their systems.

UVC is the wavelength used for Ultraviolet Sterilizers which kill harmful bacteria. This wavelength is very dangerous to all animals.

Different spectrums are required for different species who dwell in different latitudes and at different water depths in their natural environments.

Full Spectrum Light/CRI Rating

Full spectrum light is a light source that emits all of the wavelengths of the visible spectrum in proportion to that of natural sunlight. To give you the best color rendition (CRI rating) and bring out the natural beauty of aquarium fish and plants in both freshwater and marine tanks, choose a daylight lamp with a full spectrum of visible light. A CRI as close to 100 (the CRI of natural sunlight) is desirable for visual affect. Its spectrum graph would have higher peaks in the middle of the spectrum with low ends.

Kelvin Rating

The color temperature of light is the ratio of red to blue light waves measured in degrees Kelvin (K). At 6000 degrees (K), the ratio between red and blue is equal. The lower the content of blue light waves, the lower the color temperature. During the day, the color temperature of sunlight varies. It also changes at different depths underwater as reds are filtered out more rapidly than blues.

Although blue spectrums penetrate deeper into water, species which live fairly deep rarely see the red end of the spectrum because it is filtered out by the water. They can actually be "bleached" to colorless by a light that is too intense. A "K" or Kelvin rating of 5000-5500 is a good estimate to simulate a noon sun in most tropical environments.

Stimulate Spawning & Appetite

In freshwater aquariums, you may add tubes with UVA emissions (higher in blues) and you will begin to stimulate feeding and mating behavior in your fish.

Healthy Plants

To maximize the photobiological process in plants, add more red AND blue spectrum, as plants require both red and blue enhancements. The use of a floral bulb with a daylight bulb will give good visuals AND healthy plants. (Remember, if you use plant-enhancing daylight with added red and blue spectrums, you may also increase the undesirable algae growth in your tank, so don't enhance these spectrums unless you have adequate freshwater plants to battle for the algae nutrients)

Trichromatic bulbs are an excellent full spectrum daylight lamp and provide maximum daylight simulation. They are very good for freshwater tanks simulating 10-15 feet of water depth. This is best for visuals as well as brightness. Some trichromataics are also high in blue UVA emissions to stimulate feeding and breeding behavior.

Marine and reef tanks are VERY specific. A minimum of two fluorescent light sources is almost always required, and even more tubes is often beneficial.

Actinic Light

Actinic light promotes the growth of Zoaxanthellae algae, essential for the growth and well-being of all photosynthetic corals and invertebrates (not macro algae). However, Actinic and strong blue spectrum lighting is visibly blue and will definitely need a full spectrum bulb to help offset the color distortion.

If your reef or marine tank appears too blue, balance its visible spectrum with a more intense daylight bulb or add another daylight bulb to the group. 5,000K-6,000K is usually pretty good. However, remember that macro algae can be a problem. Too much "daylight" (with enhanced red spectrum) will promote plant growth, and macro-algae responds similarly. A good rule of thumb is to use one actinic lamp and one or two daylight lamps for each 30 gallons of water.

50/50 Light

The 50/50 bulbs were developed specifically for marine and reef tanks where the hobbyist wants the best of both worlds: healthy invertebrates as well as visual appeal. If you can't decide, go for one or two 50/50's.

Lighting Tips

The color spectrum of a lamp changes with age. Although it may still look like visible light, the first wavelengths to go are the blue and UVB/UVA spectrums not visible to the eye. If your lights are not changed at least once per year (preferably every 6-8 months) you are probably not getting the original spectrum of light for which the bulb was rated, and your tank inhabitants will suffer.

Deeper aquariums require extra lamps. A good rule of thumb is to add an extra lamp for each 15 inches of tank over 20 inches high so that adequate light reaches the plants or reef inhabitants which dwell on the bottom of the tank.

Glass filters out 95% of all UVB rays unless your tank's glass top has been specially produced for high quality light penetration.

The amount of time that a tank is illuminated should closely resemble the native environment of the inhabitants. Since most are tropical, a 12 hour light cycle (12 light/12 dark) will be fine. There is rarely any need for your aquarium to be lighted for more than 12 hours, and longer daylight cycles can induce undesirable algae bloom.