Aquarium Plant Lighting – 2

Providing lighting for aquarium plants.

To be continued…

There are three types of aquarium lighting fixtures: • — open suspended fixture, • — open top-mounted fixture, • — built into the aquarium hood. Practically, the choice of lamps is limited to three types — traditional fluorescent lamps, compact fluorescent lamps, and gas-discharge lamps. In the overwhelming majority of cases, fluorescent lamps are used; less commonly, mixed lighting is created by incandescent lamps (krypton lamps are the most economical), compact fluorescent, and linear fluorescent lamps.

When choosing the size, be sure to consider standard lamp lengths. It is best to focus on the standard lamp length plus clearances for the contact group or a combination of different lamp lengths. In any aquarium, you can create lighting sufficient for even the most light-demanding plant. By changing the placement of the fixtures, you can vary the lighting conditions within a single aquarium. The optimal placement of lamps is above the water at a height of 5 cm from its level. The best position for the lighting fixture is on top and closer to the front viewing glass. In this case, plants develop well and fish look more spectacular.

When illuminating an aquarium, two things should be considered. Making the aquarium deeper than 50 cm is not recommended for two reasons. Remember that the higher it is, the harder it is for the light to “penetrate” the water column, and bottom-dwelling plants may suffer from a lack of light. The emitted light should reach the bottom of the aquarium as much as possible. However, between the lamp and the bottom of the aquarium, there are various obstacles that the light must overcome. First of all, this is the cover glass, which should be regarded not only as a glass barrier, but often, especially if it is dirty, as a light filter. Secondly, this is the water mirror, i.e., the surface of the water itself. It is no coincidence that they say: the water surface partially reflects the incident light. And finally, the water itself.

With increasing distance from the lamp, the light fades quickly. With every 10 cm increase in depth in “medium transparency” water, approximately 50% of the radiation is lost. Thus, if 2000 lux is recorded at the water surface, only 60 lux will reach the reservoir at a depth of 65 cm, taking into account a 10 cm layer of substrate and 5 cm of free space above the water surface.

Most of this intensity decrease occurs because light rays are not parallel, and much of the light scatters on its way to the bottom of the aquarium. Another part of the light is absorbed by humic acids and suspended matter dissolved in the water. And finally, most of the beneficial spectrum is filtered out before the light reaches the bottom of the aquarium. The color of the water and its transparency have a strong influence on the aquarium’s illumination and spectral composition of the lighting.

The cleaner, more transparent, and colorless the water, the deeper the light penetrates, and accordingly, the brighter the aquarium plants are illuminated. The yellow color of “old water” distorts the blue part of the spectrum, turning it green, which is somewhat worse for plant perception. And finally, you must always consider the arrangement of plants relative to the light source. A fixture with fluorescent tubes across the entire aquarium provides an illumination of only 25% of the light in the corners compared to the center of the aquarium. Therefore, plants that require more light should never be placed in corners where light intensity is much lower than in the center.

Secondly, it is difficult to reach the bottom, especially near the back wall, which is often necessary during maintenance when you need to remove debris from the bottom, plant, or bury a plant. In tall aquariums, the lower layers of water are poorly oxygenated, which makes aeration with an air pump mandatory. The higher the aquarium, the more powerful the air pump needed to create greater pressure. Standard medium-sized aquariums will likely have a height of about 40-50 cm. For plants, this is already quite a lot, since creating decent illumination at the bottom of the aquarium is difficult even at a height of 40 cm. Creating lighting in a very deep aquarium is only possible using complex and powerful light sources.

In the absence of a reflector, the amount of light falling on the surface is determined by the angle between the directions to the edges of the illuminated area with the apex at the lamp. The amount of light is (depending on the lamp height and area size) 25-30%. Efficiency does not depend on the number and diameter of the lamps, provided they are placed approximately in the middle. If lamps are placed close to the edge, part of the luminous flux will be lost. Using even the simplest reflector almost doubles the useful luminous flux. Therefore, it is better to use fewer lamps, but with a reflector. The “best” reflector is only slightly (10-20%) better than the worst.

With a lack of light, plants release little oxygen, causing fish to suffocate, fine-leaved plants to die, and brown spots to form on the walls, followed by a continuous coating. If the aquarium is insufficiently lit, brown algae, colored yellow-brown, develop in large numbers. They form a brown coating on the aquarium walls and plant leaves, causing the latter to begin to die. Do not place the aquarium in bright sunlight, as green algae will begin to develop very intensively in this case. The aquarium walls and plant leaves quickly become overgrown, chemical and biological processes are disrupted, the water “blooms”, and the plants die. Determining a lack of light in the aquarium is very simple: if stones and glass become covered with a brownish coating, it is necessary to improve the lighting. If the coating is green, there is an excess of light in the aquarium.

What illumination do plants need?

Different plant species require varying lighting intensities:

As we can see, the list begins with shade-tolerant *Cryptocoryne*, many of which need so little light that they survive wonderfully in shady streams flowing under a dense forest canopy. To protect themselves from bright light, these plants contain a lot of red pigment in their leaves, giving the leaf blade brown, reddish, and olive tones. This is characteristic of many plants that find themselves in bright light, and for us, it makes these plants attractive and noticeable in collections. As you move down the plant list towards higher lighting, the plants become predominantly green. The list ends with water-floating plants and *Nymphaea*, whose leaves are always exposed to sunlight.

Providing plants with artificial lighting. The importance of lighting.

Providing aquarium plants with lighting.