You are here:  The Power of UV Light

Today, novices and advanced aquarists are achieving greater success because of two factors:
- The availability of more information about aquarium keeping
- The development of new products and techniques through research

The manufacturer of the AQUA-UV Ultraviolet Sterilizer is dedicated to both of these advancements. This information sheet is one of a series intended to better inform aquarists and shops owners so that all fish and invertebrates will live longer, healthier lives, leading to greater satisfaction and enjoyment for a concerned.

The clean, quiet and efficient way to a healthy aquarium, garden pond or professional installations

Maintaining fish in an aquarium or a pond requires that the artificial environment be held in a stable condition, free of both organic and inorganic pollutants. The water should be well oxygenated, lighted and kept at a reasonable constant temperature level.
Unfortunately, the factors contributing to the well-being of fish can be disrupted allowing the growth or increase by multiplication, of dangerous free swimming microorganism, which as proliferating bacteria, parasites, protozoa, viruses or fungus can put a strain on the well being of the fish and represent a real danger if they are not controlled.
Standard mechanical and biological filters will not eliminate the abundance of unwanted microorganisms. Ultraviolet sterilization is a proven method to control lethal organisms in fresh water and marine aquariums and is a safeguard against rapid increases of these organisms.
The importance of this feature is amplified in aquarium system containing fish that may be weak as a result of improper feeding, handling or parasites.

What is ultraviolet light
Ultraviolet light is the name given to the light waves that fall between X-rays and visible light rays in the electromagnetic spectrum. The ultraviolet (UV) light is further divided into three classifications; extreme UV (wavelength less that 2000 Angstrom), near UV (wavelength between 3000 and 4000 Angstrom) and far UV section (UV-C), which is our specific area of interest (wavelength from 2000 to 3000 Angstrom) and is classified as the germicidal region. UV light is invisible to the human eye, but consists of a high radiation energy level.

UV intensity definition

Angström - Unit of length and in our case refers to the length of the light waves generated by germicidal lamps.
- 10 Angström = one millionth of a millimeter = one nanometer
- 2537 Angström = 253,7 millionths of a millimeter = 253,7 nanometers

Microwatt ( µW ) - 1 microwatt = one millionth of a watt

Intensity ( µW/cm² - The UV light intensity of a germicidal lamp is expressed as microwatts per square centimeter.

Source of ultraviolet light
The sun produces ultraviolet light. However, by the time the UV light reaches the earth it has been reduced to minimal intensities by such factors as the atmospheric conditions, latitude, and time of the day. Artificial UV light in the germicidal region is available through the use of commercially available lamps.UV light (energy) is produced by a low-pressure mercury lamp made from a glass formula, which permits the passage of light rays of a specific wavelength. The strongest effectiveness of a germicidal lamp is approximately at a wavelength of 2537 Angström.

How UV light (energy) works
When microorganisms are exposed to this light, the UV energy causes a change in the chemical bonds of the DNA (deoxyribonucleic acid) molecules. This alteration results in their inability to multiply and therefore their elimination.
The AQUA-UV sterilizers are uniquely designed to permit the water to pass all around the germicidal lamp, taking advantage of the 360º light source. The unit will function without altering the pH or chemical structure of the aquarium water.Since UV energy cannot be stored or carried by the water, this sterilizer will not adversely affect the fish or beneficial nitrifying bacteria settled in the filter, gravel or stones and plants.
The UV light absorbed by a microorganism is a product of the time of exposure in seconds and the UV intensity at the microorganism in microwatts per cm².
The UV intensity is a term used to define the quantity of light produced by a germicidal lamp at 2537 Angstroms.
AQUA-UV sterilizers should be installed in vertical position with outlet on top.This will allow trapped air in the unit to escape. The water can be circulated through the sterilizer by a small pump or the pressure tubing of a powered filter. The UV energy generated by the germicidal lamp is transmitted through the water onto the inside surface of the canister housing, thus exposing all of the microorganisms in the water to a UV intensity. The total depth of penetration (distance between lamp and inside surface of the filter housing) varies for each model, however, the maximum depth is approximately 2,5 cm (1") on the 15, 25 and 55 watt models.

Factors that can influence the transmission of UV light in water include the clarity and existence of any particulate matter in the water. Distilled water would be the best water available. Water with a high content of particulate matter will decrease the UV transmission by absorbing the UV energy intended for the microorganisms. Synthetic and common salts do not interfere with the UV energy.
Two factors, which can also affect the overall germicidal effectiveness in water, are the lamp life and the lamp operating temperature.
Lamp Life: The output intensity of a UV lamp is reduced, as the lamp gets older.Excessive start and stop cycles will shorten the life of the lamp. Continuous operation will lengthen the life.
Operating temperature: The lamp operating temperature is controlled by the medium (air or water) next to the lamp and its relative efficiency in conducting or dissipating heat to or from the lamp surface. The best operating temperature of the lamp is around 40ºC. Operating temperatures significantly above or below this temperature will reduce the germicidal output of the lamp. Under most aquarium conditions, the germicidal lamp will operate at temperatures close to the optimum and little efficiency will be lost due to the temperature effect. Reviewing the required UV intensity values to destroy microorganisms , it can be seen that most bacteria can be killed with a relatively low UV intensity while parasites require a much higher intensity. What this means to the aquarist is that for a given AQUA-UV unit, the lower the flow rate through the unit, the higher the level of UV intensity available to destroy unwanted micro-organisms.