What lamps are used to illuminate the aquarium.
To be continued…
Metal halide lamps. One of the modern technologies is metal halide lamps. An MH lamp is a metal halide lamp belonging to HID (High-Intensity Discharge) lamps, meaning that despite their small size, they produce a very large luminous flux. These are primarily compact and high-power light sources. Metal halide lamps are a type of gas-discharge lamps because, unlike conventional halogen lamps, metal halide lamps use gas discharges rather than the thermal glow of a filament.
These lamps should not be confused with halogen lamps, which are similar to incandescent lamps and are not gas-discharge lamps. In design, these lamps are similar to mercury lamps. In addition to mercury, metal iodides are added to them. These lamps are one of the most efficient light sources. They outperform mercury lamps in luminous efficacy and color rendering index.
The second feature of MH lamps is the point-source nature of the light. A set of fluorescent tubes provides diffuse lighting; most rays enter the water at an oblique angle, and some are reflected from the water surface: the greater the difference from a straight angle, the greater the reflection. Another part, having entered the water and moving along the surface, fades after several reflections from the aquarium contents and glass. As a result, a very small fraction of light reaches the bottom.
Hence the well-known recommendation: a planted aquarium should not be more than 50 cm deep. And this recommendation is absolutely correct, but only for fluorescent lamps. An MH spotlight provides directional light that falls almost perpendicularly to the surface. As a result, the attenuation coefficient in the water column is significantly lower. Under such lamps, you can easily get lushly growing vegetation at a depth of 60-70 cm.
Lamps are available with a power from 70 to 1000 W in two designs: spherical bulbs made of quartz or ordinary glass, and cylindrical (tubular) bulbs made of quartz glass. Each wattage requires a compatible ballast. The bulbs of these lamps get very hot, and they need to be turned off periodically for at least an hour. Due to the intensive heat generation by metal halide lamps for aquariums, fixtures with these lamps must be equipped with cooling fans and mounted at a distance of 20-40 cm from the water surface to avoid overheating the aquarium water. However, the absence of an aquarium lid easily solves this problem: thanks to the free air flow, overheating of the water in the artificial reservoir is prevented.
Despite their small size, fixtures with a metal halide lamp provide excellent color rendering and high luminous flux throughout the entire service life of the lamps. They have a long service life, good color rendering characteristics, and high light intensity, which allows illuminating aquariums over 50 cm deep. Consequently, fewer fixtures can be used to obtain the desired illumination level, and these lamps have a higher lumen-to-watt ratio, which means energy savings.
In addition, an MH fixture produces more light for every watt of energy spent than the best fluorescent lamps. Metal halide lamps need to be replaced after 4,000 – 5,000 hours of operation (from one to one and a half years when operating 8 hours a day). Using a lamp until the end of its service life is unsafe, as it can lead to lamp breakage.
The design features of this type of metal halide fixtures allow them to be built into interior elements, and special reflectors form the light flux of the required dispersion angles. In swivel models, it is possible to regulate light fluxes in the right directions, creating various interior lighting solutions. Fixtures can be suspended from the ceiling or attached to the wall with brackets.
Wall and ceiling fixtures, unlike recessed ones, can be mounted using suspensions (pendant fixtures) or directly on the wall or ceiling (surface-mounted fixtures). However, under no circumstances should lighting devices be attached to the tank lid or on the lower tiers of the aquarium, as all this can cause the water in the tank to heat up and lead to the death of its inhabitants.
Ballasts for lamps are, of course, better chosen as electronic ones, and made not according to an analog circuit, but on a specialized micro-assembly. Electronic ballasts have significantly less weight and volume and extend the service life of the lamp. Ballasts are usually placed in the back of the lid, or even better, removed from the lid entirely, for example, onto the wall behind the aquarium or into the cabinet under the aquarium.
There are fluorescent lamps with T5 and T8 parameters on the market. A few years ago, a completely new type of fluorescent lamps was released – T5 with a diameter of 16 mm. It is easy to distinguish new lamps from old ones (T8 type): new T5 lamps have an outer diameter of 16 mm rather than 26 mm like the old T8. A 24W T5 lamp has a length of 55 cm, while a 25W T8 lamp has a length of 74 cm. They are labeled as T5 HO and T5 HE. T5 lamps are much more compact due to their small diameter and higher power at the same length; due to the absence of a starter, the number of wires is smaller, which simplifies fixture installation. They operate only on electronic ballasts (EVG). T5 lamps must not be used with old wire ballasts – they will fail very quickly.
All T5 lamps have a standard three-digit marking, for example, T5 860. The first digit indicates the color rendering index CRI or Ra: digit 7 – Ra75, 8 – Ra85, 9 – Ra90 and higher. The second and third digits indicate color temperature: 60 – 6000K, 65 – 6500K, 50 – 5000K, etc. That is, “965” means that this is a lamp with a color rendering index Ra greater than 90 and a color temperature of 6500K. The letters HO or HE in the name indicate luminous efficacy and power consumption. HO (high output) lamps have maximum luminous efficacy and slightly higher power consumption. HE (high efficiency) lamps have lower power and luminous efficacy. It is impossible to confuse them – they are produced in different wattages.
To solve certain lighting issues, aquarium equipment manufacturers have long been producing specialized fluorescent lamps. Some models of these lamps are designed to give your fish a brighter and richer coloration, while others are important for the successful growth of plants. A wide spectrum indicates that, unlike conventional fluorescent lamps whose spectra have a pronounced peak, the spectrum of these lamps is more or less uniform, meaning color rendering is more natural due to the presence of a larger number of colors in the spectrum.
Triphosphor or trichromatic lamps have peaks in the spectrum corresponding to the three primary colors. This improves color rendering. Such lamps have a special rare-earth halophosphorus coating. Some lamps have built-in reflectors to emit light in only one direction. There are plenty of manufacturers of such lamps on our market.
Application of metal halide lamps in fishkeeping.
Light sources. Energy-saving, Krypton, Halogen, LED lamps. 
