Lighting: Wattage and Kelvin

[cherietung]

If a tank requires 200w for a 400l tank but is capped at 144w, can this be compensated with lights of higher kelvin?

Recently saw the Zoomed Day Lights at 10,000k. Assuming I replace my Arcadia 6,500k, is this an indirect way to compensate the required wattage?

Thanks in advance.

[|squee|]

Erm... I don't think so

Light temperature ( the Kelvin thing ) is the colour spectrum of the lights, whereas the wattage can be expressed as the "power" of the lights.

The spectrum can't be increased... plants do best in 65000K. Therefore I suppose you can't increase the temperature of the lights to compensate for wattage

[PeterGwee]

144w is fine as long as the light is well spread around the tank. Just make sure no plants get shaded or place low light demand plants in those dimmer locations. (Its a maintenance issue here.. )

Plants adjust to the light spectrum given them so there is no apparent difference except to the eye. Do not use bulbs design for marine tanks though..those are not suitable. 4000K-10000k seems fine.

Regards
Peter Gwee

[greenie]

Bro, can read more here : Lights Part 1 And here : Lights Part 2

[greenie]

* Edited by vinz because the post was too long and was messing around with the page formatting. *

Also had this article saved for my reference.

Let There Be Light!

Copyright 2000 by George and Karla Booth

Humans have been using artificial lighting for a very long time. It is second nature for us to walk into a darkened room, feel for a light switch and light our way. Aquarists who have fish-only setups have been using lighted hoods for many years and don't spend much time struggling with the concept. Any bulb that fits in the hood and has a pleasing spectrum is suitable. Many of the aquarium specific bulbs are enhanced in the blue and red spectrum to bring out those colors in the fish.

On the other hand, if you visit any of the Internet sites devoted to planted aquaria you will quickly realize that lighting is a very popular topic. You will also notice that the topic seems to be fraught with misinformation, myths, wives tales and amazing claims by lighting suppliers. So why is it that freshwater plant enthusiasts end up thinking that proper lighting is "a puzzle wrapped in an enigma"?

One of the most common questions asked is "What's the best light for plants?" This question seems to get the most varied answers simply because "best" can be defined in so many ways. Are you trying to optimize intensity? Are you looking for the best spectrum for growth? Do you desire a natural appearance? Do you want to take prize-winning photos? Are energy costs critical? Is the initial expense a stumbling block? Do you have a closed hood or open top? How deep is your tank?

If you don't know much about lighting terminology and technology, these can be difficult questions to answer. But, armed with a little knowledge, you can easily optimize your lighting setup to suit the needs of your tank inhabitants and your personal preferences. Lighting can seem complicated, especially when an expert starts spouting impressive sounding terms, but it is really very straightforward.

The are many benefits associated with optimum lighting. If you are growing live plants, proper lighting is critical to good growth and plant health. If you are interested in photographing your aquariums, whether for contests or publication, good full spectrum lighting will make your job a lot easier. Finally, with the correct lighting, you will find that your aquarium, whether it's fish-only or fully planted, will be displayed at its best. Professionals in the "display" business, such as museums and art galleries, know that proper lighting is the number one way to showcase their collections. Our fish and plants deserve no less!

[greenie]

continue...

Lighting Terminology

Understanding the meaning of a few key terms is the first step in the search for success with lighting.

Watts

Bulbs come in various wattage ratings. This describes how much electrical power a bulb uses and does not describe how much light it generates. Different bulb technologies will produce differing amounts of light per watt. More technically, different types of bulbs are more efficient at converting electrical energy into light energy. For example, a typical fluorescent bulb is four times as bright as the same wattage incandescent bulb and a metal halide bulb is two times as bright as the same wattage fluorescent bulb. Even within a technology, light energy per watt will vary. All normal output 40-watt fluorescent bulbs draw 430 ma of current but vary greatly in how efficiently they convert the energy from the resulting internal arc into light.

Unfortunately for the aquarist, wattage is the simplest and most common way to specify how much light is needed even though it is not an accurate measure. It is very common to see "use 2-3 watts per gallon of fluorescent light for plants". This is a very coarse rule because it doesn't take into account the efficiency of the bulbs, the type of reflector, the form factor of the tank or the type of plants being grown. But it is a good starting point because all bulbs are rated in watts. It's the least common denominator of light bulb specifications and it may be satisfactory for a lot of plant enthusiasts.

Lumens

Lumens are is the total amount of light that a bulb is capable of generating. This information should be readily available, either on the bulb package or from manufacturer's data sheets. It may take some digging to find it though. There are two values usually quoted for fluorescent bulbs: initial lumens and design lumens. Initial lumens describe how much light it produces when first turned on. Design lumens describe how much light it will produce for a much longer term. After an initial 20% drop in brightness, the light output will slowly decrease over the lifetime of the bulb.

Lumens are somewhat misleading since they are geared towards what the human eye perceives. Human eye response is very sensitive to green light and less sensitive to the red and blue ends of the visible spectrum. Conversely, plants are more sensitive to red and blue light than green. A bulb heavily weighted to produce light in the green spectrum bands will be perceived as much brighter to the eye than bulbs that concentrate energy in other bands but plants will not be able to use much of the energy. A "Cool White" fluorescent bulb (designed to take advantage of this phenomenon) looks bright to us and has a high lumen rating but won't grow plants as well as other types of bulbs. The bottom line is that even if a bulb has a high lumen rating, it might not be suitable for aquarium lighting.

The lumen rating is a better way to specify lighting than watts since it describes how much light is available. But it still falls short in that all the lumens might not reach the plants and it doesn't describe the energy bands that are generated. A bulb might have lots of lumens but much of the light might be lost because of a poor reflector design or the light might be in a part of the spectrum where plants have poor response.

Lux

Lux is a measure of the actual intensity of the light falling on a specified area and is a much better way to describe lighting requirements. Lux is defined as lumens per square meter. Unfortunately, since lux depends on the how the light gets from the bulb to the area, the manufacturer can't specify it - it has to be measured by the aquarist. Hobbyist luxmeters are available for under $150 and are invaluable for the serious light cognoscente. Also note that since lux are defined in terms of lumens, they also suffer from a bias towards human eye response.

[greenie]

continue...

CRI

This is the Color Rendering Index and describes how closely a light source renders colors compared to "standard" sunlight as observed by a "standard" human eye. A perfect source would score 100. Full spectrum bulbs rate in the 90s. CRI is usually specified for higher quality fluorescent bulbs but does not seem to be a valuable measure for bulbs used in planted tanks. Bulbs with a high CRI may not necessarily have the right spectrum for plants and may not be bright enough for good plant growth.

Kelvin Temperature (K) or Color Temperature

This describes the overall color of the light but not the spectral components. If a light source is stated as 5000K, it is the same color as a radiating black body (a physics term) heated to that temperature. Incandescent bulbs are around 2700K (reddish), "daylight" is roughly 5500K and higher color temperatures look more blue. In an aquarium setting, daylight or 5500K bulbs may look a little yellow while 6500K bulbs have a pleasing white light.

Spectrum

This describes the wavelengths of light that make up the light source. Visible light is a continuous band of colors ranging from violet to red (wavelengths of 380 nanometers to 700 nanometers). Sunlight and incandescent light are composed of all visible wavelengths. Fluorescent and metal halide bulbs emit only a few wavelengths ("spikes"), depending on the phosphors and rare earths used. Most fluorescent bulbs emit two strong spikes to generate a particular color temperature. A newer type of bulb called "tri-phosphor" adds a rare-earth phosphor to generate a wider spectrum of light - usually three spikes - and is strong in the green spectrum. Tri-phosphor bulbs are more expensive than other bulbs but generally give a pleasing appearance to the aquarium and are well suited for good plant growth.

PAR

Photosynthetic Active Radiation is the true measure of how plants respond to light. Just as lumens are keyed to human eye response, PAR is keyed to photosynthetic response. If bulbs were rated in PAR, it would be easy to select the best bulb for plant growth (but not necessarily for good appearance). Unfortunately, PAR meters are expensive and are not generally available to hobbyists and few if any bulb manufacturers supply PAR specifications. So, until someone sees the light, we are stuck with selecting the best bulb based on the other ratings.

[juggler]

There's an interesting article which I always like to point out to folks who asked about lighting. See Lighting as a Function of Tank Size in the Aquaria of Takashi Amano.

[juggler]

greenie: The article you quoted can still be found in the internet. Can just point us the link: Let There Be Light! Copyright 2000 by George and Karla Booth.

[cherietung]

Thanks guys. I am aware of the difference between the 2 and vice versa. Due to the design constraint of the tank itself, I had no choice but to hunt for voodoo solutions that eventually led to the path of truth and reality.

There are other lights offering more than 10,000k for marine tanks. But this Zoomed 10,000k for both marine and freshwater was introduced of recent.

I was hoping for an alternative opinion that differs from the norm. The constraint of the lighting made it even difficult for me to grow E.Oriental, given by our regulator forum contributor Lawrence Lee.

My apologises if this question was raised with the misunderstanding that the writer had not browsed for similar answers.

[bclee]

[quote:221cf006e0="cherietung"]Thanks guys. I am aware of the difference between the 2 and vice versa. Due to the design constraint of the tank itself, I had no choice but to hunt for voodoo solutions that eventually led to the path of truth and reality.

There are other lights offering more than 10,000k for marine tanks. But this Zoomed 10,000k for both marine and freshwater was introduced of recent.

I was hoping for an alternative opinion that differs from the norm. The constraint of the lighting made it even difficult for me to grow E.Oriental, given by our regulator forum contributor Lawrence Lee.

My apologises if this question was raised with the misunderstanding that the writer had not browsed for similar answers.[/quote:221cf006e0]

If you have truely read and understood about PAR, colour temperature & wattage, you might have known that changing colour temperature of the lighting will have very minimal impact on the plant growth and will definitely not compensate for your lack of wattage.

You do not have to apologise, your questions and even this post do make you look that you have not understood what you read.

BC

[greenie]

greenie: The article you quoted can still be found in the internet. Can just point us the link: Let There Be Light! Copyright 2000 by George and Karla Booth.

Thanks juggler.

[cherietung]

[/quote]

If you have truely read and understood about PAR, colour temperature & wattage, you might have known that changing colour temperature of the lighting will have very minimal impact on the plant growth and will definitely not compensate for your lack of wattage.

You do not have to apologise, your questions and even this post do make you look that you have not understood what you read.

BC [/quote]

bclee:

Like I said in my post, I am looking for a Voodoo solution.

I appreciate very much that you keep your views on individual literacy ability to yourself.

Thank you and good day.

[theodore]

You should have better luck locating a witch doctor in an African-based forum.

Happy New Year!

[vinz]

Hello? It is totally unconstructive to "add fire to fire". Please refrain. Thank you.

CherieTung is just asking to see if there is a solution that he has not read of yet.

[greenie]

Yeah, no voodoo solution here, just the facts. Cool it guys.