What is light?
The wavelength of light that can be distinguished by the naked eye of a normal person is the wavelength between infrared and ultraviolet, which is probably between 450mm and 750mm. Natural light (daylight) includes light of all wavelengths, that is, all light that is visible and indistinguishable by the naked eye. Because light of different wavelengths passes through the interface (such as glass or water droplets) at different points of view, the speed is different, so the sunlight can be refracted into seven different colors: red, orange, yellow, green, blue, indigo, and purple. Visible light of colors, this is the reason why we see rainbows more often in our daily lives. It can be seen that the light formed by uniformly mixing all colors of light is white light. The share of all kinds of rays in the sunlight is so large that it is flat, but the sunlight of different latitudes is different. Because of the relationship between the thickness of the atmosphere and refraction, areas with higher latitudes are rich in blue light. According to the same principle, most of the photos under the sea are bluish, because the sea water also absorbs the non-blue light. Only the sea water absorbs the non-blue light at a much higher rate than the atmosphere, and most of the non-blue light is up to one meter deep. Before, it was absorbed by sea water.
There are many ways to measure the intensity and quality of light. Generally, the units for measuring intensity are candlelight, lumens, LUX, etc. This part is explained in many articles, so I won't repeat it here. The color of the light can be indicated by the color temperature (degrees Kelvin; oK), which is also the part that most people have more doubts about. The color rendering of light can be indicated by the color rendering index (CRI).
Color temperature
Different light has different color temperature, which is expressed in absolute temperature oK, so as to quantify the level of light. We can imagine the color temperature as an iron block being heated. When the iron block is heated to 3500oK, the iron block will appear orange-red light; when the iron block is heated to 6000oK, it will appear white light. When above 1000oK, blue and white light will appear, so the color temperature of sunlight is about 5000oK~6000oK. Therefore, we can roughly distinguish the scale of the color temperature of the light declared by the light source. For example, a light bulb that declares yellow light should have a color temperature around 3000oK, and a light bulb that declares white light should be around 5500-6500 oK, and it declares blue-white light. The light bulb is about 10000～14000 oK, if it is a light bulb that announces blue light, it is about 20000 oK.
Color rendering pointer-CRI
Color rendering can be used to identify the change in the chromaticity of an object under the projection of a fixed light source. In other words, color rendering is the chromaticity of the color of an object under the irradiation of light. The color rendering pointer is between 0 and 100. When the color rendering pointer is at 100, it indicates that under this light, the color of the object is its original color, and the color of the object has not been altered by the light. Generally, lamps with a color rendering value around 90 have excellent color rendering properties. Assuming that the color rendering pointer of a light source is very low, the object irradiated by this light will have colors and shadows that are different from the primary colors. Light with high color rendering: sunlight, and some fluorescent lamps, such as fluorescent lamps. The color rendering of Gro-Lux, or sodium vapor lamps (sodium vapor lamps) is very low. Generally speaking, more reputable manufacturers will indicate their color temperature and color rendering properties on the lamp manuals they spend.
The following is a comparison of light sources one by one
Natural light
It is a very outstanding light and can be used for free, but the disadvantage is that it is very difficult to control! Sunlight is the most familiar light source for fish and plants, and it is the most natural lighting method. But if you want to gather satisfactory sunlight all year round above the water tank instead of on the side of the water tank, there will be a moderate degree of difficulty. For aquariums, sunlight is of course the cheapest light source, but indoor sunlight is not very stable, and it is also very difficult to control. And because the latitude is different, the illuminance will also change. Assuming that you are at a higher latitude, or the tank is placed in an exposure room, or a poorly illuminated room, artificial light sources must be used instead. Sunlight is rarely used as the primary source of light for the aquarium, but it can be used as an auxiliary light.
Halogen bulb
In addition to ordinary incandescent bulbs, another type of incandescent bulbs is halogen bulbs. This kind of light bulb was developed by the American Unique (GE) Company in 1958 to make the tail light of the Boeing 707 aircraft and to improve the original incandescent light bulb. The tungsten filament of the original incandescent light bulb will evaporate after a period of use. Moreover, the glass inside the bulb accumulates a layer of evaporated tungsten, which weakens the illuminance of the bulb. In the halogen bulb, a halogen gas is involved, which may be bromine (Bromine) or iodine (Iodine). These halogen gases will be separated from the evaporated tungsten and form tungsten bromide and tungsten iodide. The chemistry of tungsten bromide and tungsten iodide is very close to that of tungsten wire. In the meantime, the tungsten can be restored to tungsten, and return to the tungsten wire, and continue to calm down. Halogens such as bromine and iodine restore the cost of the gas and continue to be separated from the vaporized tungsten. Such a chemical reaction must wait for the temperature to rise above 93oC (200oF) to occur. Of course, the brightness of halogen bulbs is 25% to 30% higher than that of ordinary white light bulbs, but the declared heat will have some influence on the water tank, which needs to be carefully considered. In addition, the space required for the chemical change of the halogen gas is very small, so the halogen bulb is generally very small, but a larger glass bulb is placed on the outside, which is mainly used for heat insulation. The life of a halogen bulb is about two thousand hours.
Light spectrum
Generally, the spectrum of artificial white light bulbs (including incandescent bulbs and halogen bulbs) tends to be red light. The color temperature of an incandescent bulb is only 2700oK; and the color temperature of a general halogen bulb is only around 3000oK. Their color rendering properties are all 100 CRI, but the green light content is almost zero.
Illumination power
The biggest disadvantage of artificial white light is that the power is not high! Compared with the input energy, the obtained illuminance is really too low. Follow the increase in bulb wattage. Its power is also added. For example, the measurement of a 100-watt bulb is much higher than the brightness of a 50-watt bulb. Another big disadvantage is that those energy sources that are not converted into light will be distributed as heat energy. Even a light bulb with the smallest wattage can also declare a lot of heat. When using it, you must think about the effect of this heat on the tank. Because the bulb will have a high temperature, if it is depleted by the water in the tank, it may cause the bulb to split, so be careful.
The power of halogen bulbs is much higher than that of ordinary bulbs! The luminosity and lifespan of halogen bulbs are longer than those of ordinary bulbs. When the life of the halogen bulb is about to expire, it can still declare the original 95% luminosity, and the service life is twice that of ordinary bulbs. But the price is also more expensive. The biggest advantage of general light bulbs is that they are cheap and easy to obtain. They are sold in almost all shops. Halogen bulbs are five to ten times more expensive than ordinary bulbs, and they can generally be found in larger shops. The primary use of such bulbs is searchlights. For aquarists, low-wattage bulbs are more useful. This type is the cheapest among the halogen bulbs, and it can be used as an auxiliary lamp for adding a fluorescent lamp lighting system. Osram has produced many different styles and sizes of halogen bulbs. Most of the shape resembles a vacuum tube. Because these bulbs are small in size and have a variety of wattages (from low wattage up to 150 watts), they are very easy to use for aquarium lovers!
Fluorescent lamp
The use cost is low, but the equipment cost is high! Fluorescent lights are not unfamiliar in our usual days. Under the same power consumption, the light they announced is four times that of ordinary light bulbs, so it is more economical to use. The fluorescent lamps that the general public are more familiar with are the more common cold light (white light) lamps and warm light (yellow light) lamps. Originally there are many different styles of fluorescent lamps! The fluorescent tube has a positive pole and a negative pole, which are in a semi-vacuum state and are rich in a small amount of mercury gas. When energized, the mercury gas will be polarized and emit ultraviolet radiation. A layer of phosphor is coated on the tube wall inside the tube. When the phosphor powder is affected by ultraviolet radiation, it will announce visible light. As for the color of the announced light, it is related to the chemical composition of the phosphor powder on the tube wall. Of course, the power of fluorescent lamps is very high, but because the positive ion depression is a natural phenomenon, after a long time of use, the current that can pass through the mercury gas will become less and less, and the power of fluorescent lamps will also become less and less. The brightness of will also increase gradually, until the sudden disappearance stops. As far as general indoor lighting is used, this does not have much impact. But for aquariums (especially when cultivating light-needing organisms), because the brightness of fluorescent lamps increases exponentially, it is best to change fluorescent lamps every six months, or at least once a year.
There are two options for fluorescent lamps: Conventional ballast and Electronic ballast. Of course, the electronic type is more expensive, but the power consumption rate is lower and the heat generation rate is also lower. Inverter fluorescent lamps will initially attenuate at 120 Hz. And this is the lowest limit that the human eye can divorce. In fact, both the illuminance and frequency of light will attenuate. Even if human eyes cannot distinguish, it does not mean that other creatures cannot distinguish or will not be affected. Electronic fluorescent lamps will only initially attenuate at 30 KHz.
Types of fluorescent lamps
There are many types of fluorescent tubes, with different sizes, chemical compositions of phosphor powders, and various wattages. But the most common type is the standard (T12) four-inch tube. The diameter of this type of tube is 1.5 inches, and the length is 18 inches, 24 inches, 36 inches, 48 inches, 72 inches, and 96 inches. The diameter of the T8 or slimline tube is one inch wide, and the length is 24 inches, 36 inches, and 48 inches. In addition to the straight tube, there is also a U-shaped (PL lamp) tube with a length of about 24 inches. Round lamps have many different widths. In the past few years, mini fluorescent lamps have become very popular and have gradually replaced white light bulbs. There are many styles of this kind of lamp, ranging from a 3.5-watt bulb to a 40-watt four-inch lamp, but the size is only one-third of that of a normal fluorescent lamp. For small aquariums, the most suitable bulbs are: HO (High Output) and VHO (Very High Output) tubes. The power consumption of the VHO lamp is very high, but the light attenuation rate is lower than that of the general T12 lamp. The chemical change and attenuation of phosphor in the lamp tube has a direct effect on the combination of the light spectrum. The fluorescent lamps that can satisfy the lighting needs of the aquarium only account for a small part of the commercially available products. Generally speaking, industrial lamps (industrial), full spectrum lamps (full spectrum), fluorescent lamps (daylight), plant growth lamps (plant growth), chemical lamps (actinic), tri-phosphor lamps (tri-phosphor), special The special purpose and HO/VHO lights can meet the requirements of the water tank. (Note: Some of the above lamps are not sold in general wholesale stores.)
Industrial tube
Industrial lamps include cold light and warm light that are often used in lighting systems in homes and workshops. These bulbs can convert the minimum amount of electricity into the highest brightness. Because human eyes are most sensitive to green light, many of the spectrum of this kind of bulbs are concentrated in the green light wave, and the spectrum on both sides of the green light wave rises and falls sharply. As for the spectrum of warm light lamps, it is more inclined to the end of the red light wave.
Assuming you only need to illuminate your aquarium, this kind of bulb is very suitable. The price of this kind of bulb is not expensive, and the appearance is pretty good. Of course, the primary light required for plant light and function is red light and blue light, but recently it has been discovered that many plants need the full spectrum to open the stomata on the leaf surface and cause respiration. This is why some people can grow plants in water with only cold light or warm light. As long as there is enough light, any kind of light can grow plants very well. Assuming that the plant-specific lights are used again, the growth of the plants will be very good.
Solar tube
The solar tube is an improved fluorescent lamp that is close to the natural sunlight spectrum. This was due to the new phosphorus compounds. Of course, the spectrum of light announced by the solar tube still cannot completely match the spectrum of sunlight, but it is much better than the cold light and warm light previously mentioned. There are many on the market, but the price is higher than cold light and warm light.
Plant growth light
This kind of lamp is a Gro-Lux (tm) lamp developed by Sylvania. It is very different from other lights! Apart from promoting the growth of plants, there is no other use, and no one uses it as indoor or outdoor lighting. The plant growth lamp produced by Unique Company is called Gro-N-Sho. Other plant growth lamps seen on the market are all this kind of lamps. Only the pet aquarium shop renamed and packaged them. The spectrum of Gro-Lux lamps has two peaks: one in the blue wave region and the other in the red wave region. Except for these two areas, almost no light of other wavelengths occurs, so it looks slightly purple and not very bright. The peaks appearing in the blue wave zone and the red wave zone are very concentrated. This kind of spectrum is determined by the level of absorption of different light by chlorophyll in the test tube. Sylvania company calls it Gro-Lux Wide spectrum lights, and unique company calls it Gro-N-Sho Wide Spectrum lights. This kind of light looks more pinkish than purple, and the light is brighter. The plant growth lamp made by Philips is Agro-Lite. It is a little different from Gro-Lux's broad spectrum lamp. According to the test results, the growth rate of crops under the illumination of Philips Agro-Lite lamps is 2 to 10% higher than that of other lamps. Because this kind of lamp is often used to illuminate indoor plants, there are many on the market.
