Lighting in the aquarium is necessary for both fish and aquatic plants. In the process of photosynthesis, aquarium plants absorb carbon dioxide from water and release oxygen into water, which is necessary for fish to breathe.
For good growth of plants, so that they actively multiply, the aquarist should organize high-quality lighting in the aquarium.
Normal daylight will not allow high-quality coverage of a home aquarium, because the reservoir does not produce sufficient uniform illumination, and the length of daylight will depend on the time of year. If your aquarium will be in direct sunlight for several hours, then you are guaranteed green algae and water will bloom.
Therefore, if there is no other place, like near the aquarium window, you should cover it with thick sliding curtains or blinds.
But this does not say that the sun rays should not fall on the aquarium, you can, just not more than 2-3 hours a day. To ensure a normal life of a closed ecosystem, forced artificial lighting is installed in aquariums.
As a rule, light sources are fluorescent lamps. Incandescent bulbs are not used now in aquaristics, as this is already the last century.
Now LED lamps come into vogue, which are more economical in terms of electricity consumption.
How to provide your aquarium with the optimal amount of light? Numerous sources for aquarism say that when using fluorescent lamps per 1 centimeter of the length of an aquarium with a height of 40 centimeters should be 1 watt, or if in a simpler language, there should be at least 0.5 watts of light per liter of volume.
The absorption spectrum of chlorophyll in leaves has two maxima. Chlorophyll is a substance due to which nutrients are formed in the leaves of a plant during photosynthesis. And these two maximums lie in two areas: orange-red and violet-blue.
It was found that the absorption of light in the orange-red region is several times more intense than in violet-blue. Renders, orange-red rays contribute to the active growth of plants, and purple-red – their active reproduction.
Today you can find various fluorescent lamps with different types of radiation spectrum on sale. When selecting llamas for an aquarium, you should be guided by the requirements of plants to the radiation spectrum.
Since the bulk of aquarium plants come from the tropics, the preferred length of daylight is 12 hours. For plants submerged in water, it is even shorter, since at dusk and dawn the light retains on coastal vegetation and is reflected from the surface of the water.
Based on this feature, the length of daylight hours should be 10-12 hours, and in the evening include only a weak lamp. Keep in mind that with a longer light day, algae may appear in your tank, and there is no need to do this.
The fact is that the intensity of photosynthesis sharply decreases in tropical aquatic plants after a 12-hour daylight hours, while in algae it never changes and they continue to consume nutrients from the water.
When arranging any aquarium, you must consider several factors that weaken the effect of light.
Light Absorption in Reflectors
To increase the reflectivity of the surface, you can use the installation of mirrors in the lid. If the cap does not have a mirror-like surface on the lamp side, you can use aluminum foil or polished aluminum, as they have quite decent reflectivity.
Air heating in the reflector
Fluorescent lamps work best at air temperatures of around 25 degrees Celsius. As the air temperature increases, their luminous flux begins to decrease. To avoid losses in the light flux, air vents are made in the aquarium cover for air circulation under the lamp.
Also, there should not be control gears under the cover near the lamps, since they also heat the air quite well.
Losses from cover glass
If the aquarium is covered with a cover glass, but the lid is equipped with a reflector, the luminous flux will not drain much. But if dried drips of water and other things appear on the glass, the luminous flux will decrease.
To prevent this from happening, the glass must be cleaned regularly.
Over time, the luminous flux of any fluorescent lamp will begin to decrease and after half a year of continuous operation, it is desirable to change the lamp to the same. But you should not do the replacement of all the lamps, since you will immediately have a sharp change in illumination and this may adversely affect aquarium plants.
Water column loss
As the light passes through the water, its effect weakens. No exception is even distilled water. In the aquarium water there is waste of aquarium inhabitants and plants, and the loss of light at a depth of water column of 40 centimeters is about 50%.
To reduce these losses, in the aquarium it is necessary to carry out regular cleaning and change fresh water.
Unfortunately, it’s almost impossible to give exact recommendations for an aquarist on the choice of lighting, because in two equally equipped aquariums I will have different hydrochemical, biological and other processes. Each more or less experienced aquarist selects lamps based on his experience and the various recommendations of more experienced comrades, and over time to adjust light sources.
In the newly launched aquarium, it is impossible to establish how correctly you have chosen the sources of light. But after a month or two of life of the aquarium, according to the state of long-stemmed plants, you can make any preliminary predictions about the correct selection of lighting.
If the distance between the rosettes of leaves is no more than one centimeter and the leaves are of normal color and size, then there is nothing to worry about.
If the main stem of the plant in the area near the ground does not have leaves, then there is not enough light in the aquarium. The signal that there is a lack of light in the aquarium is the length of the internode 3 centimeters or more.
But, this symptom is observed not only in aquariums with a lack of lighting, an incorrectly chosen radiation spectrum can also lead to similar problems. In this case, it may be worthwhile to add some orange-red rays and change the type of lamps.
Weak plant growth tells us that there are too many violet-blue rays in the emitted spectrum. Accordingly, you will have to replace the lamp type with another one, with a larger share of the violet-red spectrum.
If the leaves of the plants have small leafy plates, it means that either they do not have enough food, or there is too much light in the aquarium. Before changing the lamps in the aquarium, try changing the water and applying fertilizer. If this event did not help, try to weaken the light: as an option, place a plant of a floating plant above a given plant (Guadalupe naiad or pistis).
If this does not help, then reduce the number of lamps in the aquarium and look at the result in time.
According to the German colleague Horst, the amount of oxygen dissolved in aquarium water may be a sign of properly organized lighting in the aquarium. If at the beginning of the daylight, the amount of dissolved oxygen is not less than 5 mg per liter of water, and in the evening after turning off the light 8-10 mg, then the lighting you picked up correctly.