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04 - Light

LED Leuchte von Kessil

If you have a choice, you are spoilt for choice. There are many options for lighting, whereby T5 lighting has been replaced in many cases by modern LED lighting alongside the familiar HQI. We would like to briefly discuss LED lighting at the end of this report.

Light in the reef aquarium

Light is life. These three words, which contain so much truth, have been used before, and we do it again here. No wonder it cannot be expressed more aptly. Light is truly alive and very important in a reef aquarium.

Since we have now described everything in the initial phase, the question of light undoubtedly comes before the further steps of technical equipment. What type of light do you use in the reef aquarium...

No doubt this question will come up, especially for those switching from freshwater. Can I continue to use my existing Röhren or lighting. This question arises when you convert an existing freshwater system into a seawater system. In itself, the question can be answered in the affirmative; it is certainly still possible to work with the now somewhat outdated T8 lighting. However, we would only consider this lighting to be sufficient for aquariums with a height of 50 cm at the most. A lot certainly depends on the desired stock. As soon as light-hungry small-polyped stony corals move in, you are already at the end with the type of lighting, it is simply not sufficient in the long term to keep the animals species-appropriate.


Unterschied T5 zu T8

A slim T5 with 16 mm diameter and a T8 Röhre with 26 mm diameter. Note: The T8 lighting is conventional fluorescent tubes that have a diameter of 26 mm. The newer fluorescent tube, named T5 by Osram, is considerably slimmer, with a diameter of only 16 mm.

The advantage of the T5 tube, which has been known for several years, is its "slimness", which makes it possible to install more lamps above an aquarium. In addition, the use of electronic ballasts increases the output enormously. The T5 lamps are also getting better and better as the manufacturers get more and more practical and as aquarium enthusiasts become more demanding. However, they only last about one year. After one year, every light source should be replaced, regardless of whether it is an HQI bulb or a T5 or T8 tube.

Only tubes designed for marine water should be used. In practice, this means that the Röhren should have a Kelvin number of approx. 10,000 K to 15,000 K. You should bear in mind that you should not only use white tubes, but that blue tubes also play an important role. It's all in the mix! For example, at a depth of only a few metres, the red content of the water disappears. Next, at about 5 metres, comes the yellow component, and from then on all fish look grey to us.
So in practice it has proved good not to use pure white tubes, but to use the combination of white and blue to simulate a pleasant spectrum. It should be noted that there are also already mixed Röhren, which have a 60 percent share of white and a 40 percent share of blue combined.

Unfortunately, the T5 Röhren develop more heat than T8 Röhren, which could lead to problems in closed covers. A fitted PC fan for the exhaust air would be advisable here. T5 lamps are now even available dimmed, so that you can easily simulate sunrise and sunset. In addition, T5 halogen lamps have been available for some time, which are at least an optical alternative to the bars.

Not only the tube is responsible for the good light output, the reflectors used also play a decisive role. In a test, for example, it was proven that only the reflectors are responsible for the good light output, which is in some cases more than three times that of the naked tube. We also recommend the use of single reflectors, i.e. each tube has a reflector. There are so-called halogen lamps that use only one complete reflector, but in our opinion a lot of light is lost!

Following are some possibilities offered by the trade. The pictures are from Welke Lünen, where we were kindly allowed to take pictures.

T5 Leuchte von unten

1000 Watt Strahler HQI


HQI mit Röhren

For the sake of order, let's move on to HQI luminaires, which were often used in the past. In the years since LED has become the talk of the town, this has decreased considerably. 

What are HQI luminaires? Actually, the term HQI is not quite correct, but it has become established over time. The term HQI describes a type of lamp from a company... However, HQIs are quite simply metal halide lamps!


Giesemann HQI

There are not many differences in the burners (light sources for HQI lamps). The trade offers both plug-in bases and screw bases. The conventional lamps offer a Kelvin number ranging from approx. 5600 Kelvin (daylight) to 20,000 Kelvin. The light of the 20,000 Kelvin lamps is very blue. The range between 10,0000 and 14,000 Kelvin is particularly suitable. The less Kelvin, the more yellow the light. When using burners with a spectrum similar to daylight, it is advisable to add blue Röhren. Only then will you achieve a spectrum that is good for our eyes. There are bulbs with the following wattages:

70 Watt - 150 Watt - 175 Watt - 250 Watt - 400 Watt - 1000 Watt.

For aquariums up to 50 cm high, bulbs with 70 or 150 Watt are suitable. For aquariums from 55 - 60 cm high, 250 watt burners should be used. From 70 cm upwards, 400 watt burners can be used. If the aquarium is even higher, then the 1000 Watt burners remain. A one hundred percent recommendation or specification can only be made if you know what you want to maintain. Fish tanks do not need as much light as corals...

Which burners/stoves should be used for which tank mass?

We can recommend without hesitation T5 Röhren for basins with up to 75 cm height, an illumination down to the bottom is thus guaranteed at all times. Since fluorescent tubes shine brightly, it is best to illuminate the entire mass of the aquarium. HQI lamps, on the other hand, illuminate only a few spots.

Tank dimensions: 100 cm long: 1 HQI bulb
Tank dimensions: 120 cm long: 1 - 2 HQI bulbs
Tank dimensions: 150 cm long: 2 - 3 HQI bulbs
Tank dimensions: 160 cm long: 3 HQI lamps
Pool size: 200 cm length: 3 HQI lamps

Because of the emission of UV radiation, HQI lamps should always be 25 - 30 centimetres above the water. This is especially important when changing the old lamps and replacing them with new ones. In the first few days it is advisable to turn the lamp up a little so that the animals can get used to the "more intense and stronger" light.

Now you have to decide for yourself which type of lighting you want. T5 tubes are hardly inferior to HQI lighting in terms of light output. It is impossible to say which is better, there is not THE right lighting for the reef aquarium. Fluorescent lamps are generally cheaper to buy and operate, but HQI lamps offer the very important flicker and flicker effect that many people know from the sea. In addition, HQI lamps have the advantage that the tank is open at the top and it is easier to reach into the tank, which makes regular maintenance work much easier.

We hope to have helped some "advice seekers" with this little guide. For more detailed information, please contact your specialist retailer, who will also be able to show you which types of lamp are available.

Update on LED, which did not really exist at the time of writing


In addition to the types of lighting described above, LED lighting has made its way into reef aquaristics since 2009. We would like to point out here that it is best to use a luminaire that illuminates the whole area, i.e. not so much with strong spots, but with many LEDs distributed over the whole area. In addition, the beautiful blue light is not equally suitable for all corals. During the dawn and dusk phases it is ok, otherwise you should aim for sunlight. Do not light the aquarium too blue. Your animals will thank you for it.

Here are a few examples and their possibilities (app control etc)


LED Leuchte von Kessil

Steuerung über App


Frank Diehl, Robert Baur-Kruppas


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