Lighting for Freshwater Aquariums - Necessary for Aquarium Plants
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Planning the right illumination for your aquarium, you could think that recreating the sun spectrum (that is the same light of the one produced by sun) is the most important goal to reach; however this is not right, because animals and plants living in different waters, receive the sunlight in different ways (think about animals living in clear waters and those living in a deep dark waters), moreover there is not yet a kind of lamp able to recreate totally the sun spectrum.
Buying a lamp you surely would find various informations about the kind of it’s illumination, and some of them can be not easily understandable; for aquariums, it is important to know the colour temperature and the Ra value.
The colour temperature is the colour, emitted by a lamp, that the human eye can see; we talk about temperature because, technically a black object (an ideal object able to adsorb every radiation) should reach a determined temperature to show the colour emitted by the lamp. In example a 3000°K lamp emits light near red, this mean that the black object should reach the temperature of 3000°K to show that reddish colour. Usually the higher the temperature is, the more the light tends to blue colour. Anyway this information is not enough to determine if a lamp is good for our aquarium, because lamps with the same temperature and colour could have a different spectrum and one could be better than the other.
The output colour of lighted up objects is another information you should bear in mind. As mentioned above, two lamps with the same colour temperature and emitting at our eyes the same colour could light up objects in different ways (for example looking more red or green or blue). This happens because their spectrum of emitted radiations is different. For this valuation is used the index of output colour Ra, which maximum value is 100. Each lamp’s Ra is determined by comparing the colour of the lighted standard object with the colour of the same object lighted by a reference lamp. The more the Ra of a lamp is near 100 the more its light is close to the sunlight spectrum.
Incandescent bulbs are the most common lighting system you can find, and maybe it is also the cheapest one; moreover this kind of lamp for house use usually have a Ra really near 100, anyway they are not suitable for aquariums because their colour temperature is too much low, and usually is near 2000°K – 2800°K showing a colour near red without blue tones.
Neon tube lighting
Neon tubes are the most used lighting system in aquariums, this is because you can find a great number of tubes with different characteristics that can be suitable for every tank situation. It is important to choose a neon tube with at least a Ra value of 90, because the deficiency in the spectrum could create problems to plants and helps algae proliferation, since they can provide for this lighting problem. To avoid the problem it is recommended to use two neon tubes with similar Ra and different colour temperature, so one can provide for the other deficiencies. For example using two neon tubes with Ra above 90 and one with a colour temperature of 4000°K and the other with a temperature of 5500°K, the result will be a good illumination not too much blue or red.
If you have a standard aquarium, with a good number of plants, no matter if you are just starting or are experienced, neon tubes can be a good solution for:
- the great number of neon in market, - their advanced technology reached, - the affordable price, - their use suitable both in closed and open aquariums.
Having the possibility to choose among various brands you can decide the price as well. You can choose neon tubes of general brands like Osram or Philips, or brands dedicated to aquariums like Dennerle, Tetra, Aquarium Systems and others. Choosing the neon tube, no matter what the brand is take a look on the Ra and colour temperature, not only to its name. For example, tubes marked as “plant stimulants”, which have a light nearer red than blue, have been developed for land plants, and are not suitable for aquariums because they are a cause of algae overgrowing.
HQL lamps contains metal halides and are the lighting system with a Ra value nearer to 100. This kind of lamps can give great results in aquariums rich of plants, because their special structure emits rays of light that light up objects in a way really similar to the sun natural lighting; this mean that light is emitted from a point and is directed to another point and create alternated zones of light and dark, while in neon tubes the emitted light is not concentrated in a single point. This kind of lamps have anyway some troubles:
- due to their high lighting power they are not suitable for small aquarium and it is preferred to use them in tank of 150 – 200 litres at least,
- their employ in aquariums is quite recent and there are only few brands that commercialize them, with a quite expensive price,
- to use them you need a special lighting structure that filtrates the emitted UV, and are expensive as well,
- they can not be used in closed aquariums.
Those listed above are not real problems or deficiencies of the lamp, but they point out that this lighting system is not meant for standard aquariums, but for a big tank highly populated of plants that need a great amount of light to recreate a natural illumination.
Copyright note: This article is originally written by Michela Ferretti. Aqua-fish.net owns the full copyright of this article.
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