The meaning of Lights?

[MizTanks]

I would very much like to learn the meaning of lights in regards to reef keeping. What does par mean? What does nm mean? Wave lengths? What light is best for a reef system? If I can use all types of blues in my fixture and still grow corals, why is there white lamps? Are they called bulbs or lamps? What does t5 mean?
If CF's are no good (according to the census) why in the reef keeping world do they still make them. On the box of a new bulb it shows a chart with color spikes. What is this showing me? What should I be looking for when it comes to the best bulbs?

What is wrong with these lights for reefing or are they for fish only? I'm not looking to buy just to learn.
http://cgi.ebay.com/24-Inch-2x65-Watt-AquaticLife-PowerCompact-CF-Light-Fi-/350341767782?pt=LH_DefaultDomain_0&hash=item5191ff2266

I'm not sorry for all the questions :silly:

[creefer]

I can't speak to the link you have but I can say this....

PAR = Photoactive Radiation I believe.
NM = Nanometers
Lamps would be the correct terminology
T5 is a type of lamp. There are T8 and T6, etc. Primarily related to the lamp size I believe
chart with spikes is identifying the color temperature of the lamp. This is somewhat misleading because it is measured in degrees Kelvin, which is a measurement usually related to the color of steel when heated to super high temps that make it glow.

HTH...

GL

[evilc66]

Well, there is an awful lot to light, and how it can be effective for our tanks. I'll start with answering your questions, and we can go from there.

What does PAR mean? -
PAR stands for Photosynthetic Active Radiation. It's a measuerment of the number of photons between 400nm and 700nm, which is the range of visible light. It's a measurement used to estimate the growth potential of a light source. It can be a useful measurement when comparing different lights, but shouldn't be taken as an absolute measurement. Reason being is that all photons in the visible spectrum are all treated equal. Corals don't use all photons equally for photosynthesis, so PAR measurements don't always show the true nature of the light.

What does nm mean? -
Nm stand for nanometers (1x10^-9). In this application, it's a measurement of the wavelength of the light. Visible light goes from 400nm (violet) to 700nm (deep red). Below 400nm, you have UV-A (315-400nm), UV-B (280-315nm), and UV-C (100-280nm). Above 700nm, you have infrared light.

What is a wavelength? -
Wavelengths are measured in nanometers, and represent the different colors of light in this application. For example, light with a wavelength of 455nm is what we consider royal blue in the LED world. 525nm is green, and 630nm is red. Now, colors span a range of wavelengths, and change their hue depending on the direction you go. If we start with 455nm (royal blue), and add 20nm, you get into the cool blue range. Subtract 20nm, and you have deep blue/violet.

What light is best for a reef system? -
That's a highly debatable topic. There are so many options out there, and all of them have their pro's and con's. Many consider metal halide to be the "best" type of lighting, but it doesn't mean that everything else is crap. There are so many factors to consider when comparing lighting types, that we could be here all day. I'll give you a brief run down of what is commonly available:

Metal Halide:

High output
Decent efficiency
Pleasing appearance
Good overall color
High heat
12 month bulb life


T5HO (NO isn't powerful enough for reefs):

High output
Higher efficiency than MH
Wide variety of color options
Less heat than MH
8-12 month bulb life
Highly dependant on reflector quality for performance


Power Compacts:

Medium-high output (depends a lot on the bulb)
Similar efficiency to T5
Cheap
Bulbs come in smaller sizes than T5
Limited color selection
Poor performance compared to T5 because of bulb restrike issues
Reflectors don't help as much as they do with T5 (has to do with bulb shape)
6-8 month bulb life on average


LED:

Extremely high efficiency
Low power consumption
Easily controllable for intensity and color temperature
Extremely long life (50,000 hours)
No heat radiated directly into the tank
Higher complexity
High upfront cost


If I can use all types of blues in my fixture and still grow corals, why is there white lamps? -
Just saying "blue lamp" is a little ambiguous. There are blue actinic bulbs, and there are blue, or high kelvin daylight bulbs. Big difference between the two. A blue actinic bulb is typically just for color, although it does add some PAR. "Blue" daylight bulbs, like the ATI Blue+ are really just high kelvin whites, but they have properties similar to the blue actinics. They have a lot of blue output, which helps with fluorescence, but the PAR levels are much higher than a typical actinic. These bulbs have come into existance because of the average aquirists love of blue looking tanks.

What does T5 mean? -
T5 designates that the bulb is a tube (the "T" part), and 5/8" ("5" eighths of an inch) in diameter. This is a common way to describe a lot of different bulbs. T12s are 12/8" (1-1/2") in diameter. PAR lamps are the same way, but PAR stands for Parabolic Aluminized Reflector. On a PAR38, it means 38/8" (4.75") diameter.

If CF's are no good (according to the census) why in the reef keeping world do they still make them? -
They are cheap, and still come in sizes that T5's don't. Now, not all PCs are created equal. The vast majority are so-so at best in terms of output and color. Newer bulbs like the UVL PC-Rs are much better than your run of the mill Coralife. They use better phosphor blends that increase output, offer better color, and longer life. They still have their limitations, but really aren't built much different than T5s. The big shortcoming with PCs is their shape. Having a pair of tubes side by side causes what's called restrike. What that means is that light emitting from the top side of the bulb hits the reflector and is reflected back onto the bulb, and not into the tank. That light is lost, or at the very least, much less effective. UVL tried to combat that by actually integrating the reflector into the bulb itself, preventing light from actually being emitted from the top side of the bulb.

On the box of a new bulb it shows a chart with color spikes. What is this showing me? -
That is the spectral plot of the bulb. It will give you an idea as to what wavelengths of light are being emitted, and at what relative intensity. To most people, it doesn't mean a whole lot. As you start to understand more about light and what our corals need, you can start to gleen information from that chart, and get a basic idea as to how beneficial the lamp can actually be.

What should I be looking for when it comes to the best bulbs? -
High output, good color, and long life. Most of this has been tried and tested, so you can easily find out what is good/bad/otherwise. Cheap bulbs are typically just that. Cheap.

What is wrong with these lights for reefing or are they for fish only? I'm not looking to buy just to learn.
http://cgi.ebay.com/24-Inch-2x65-Wat...item5191ff2266
Provided that you work within the limits of the lamp, there is nothing wrong with them. You aren't going to be keeping a 24" deep sps dominated tank with those, but you should have good luck with an 18" deep lps/softie tank.

[tankdude]

Thanks for all the great information on lighting evilc66.

[evilc66]

Believe me, there's a lot more. I'd be happy to answer more questions on the subject, but we need to keep the subject fairly well focused. I don't want to see questions like "what T5 bulb combo should I use?"

[iyachtuxivm]

Great info always nice to see someone willing to help out!

[evilc66]

tankdude, where in Shelby are you? We've probably tripped over each other in Kee's. Heading there after work as a matter of fact.

[Heidi]

I wonder about light a lot too. I hope this question is direct enough here goes:
I have a MH 250 pendent it came with a 20,000K lamp.
1.Do any coral need more then this lamp? Is there any color of light I should be adding to this for my corals health? (I am not terribly concerned with the way everything looks just yet, I really want to just grow my coral).
2. My lamp came w/ the fixture so I figure it's elcheapo. How do you know when you need to replace your MH lamp, do they burnout like a normal light bulb, dim, or is it just a timed thing like after 12 months you replace it?

Thanks again for your help!
-Heidi

[creefer]

Evil...

Thanks for clearing up my mistakes. And, thanks for the great information.

[MyNemesis]

Is this where we cast a vote for a lighting "sticky"?

[MizTanks]

Evil, I don't know how to thank you (((((hugs))))) how's that, lol. I have learned much from you today. I now feel that I am capable of choosing the correct lighting for what I would like to grow in my tank, and what I shouldn't try without the proper lighting.
Of course I will read this many times. Just another reason for me being here at CR. One thing I have learned, that I've never really delved into until now. Is knowing about the corals I wish to keep, their requirements when it pertains to light and how important it is to research them all.

Thank you again for this wonderful explanation of LIGHTS!

Jamie.

[MizTanks]

I'm truly trying to understand what would be the best light source in a lamp that I could run for the betterment of my corals that depend on photosynthesis as their food source.

There is a shop here that is totally dedicated to lights for growing indoor plants. I've stopped in with my corals in mind. They deal only in MH and LEDS, sadly I could afford neither.

What do MH and LEDS offer that other light sources don't? Is it their high par, high kelvins?
What does *watts* have to do with coral growth is anything? i.e. 150~250~18~24, ect ect.

Thanks again Evil

Jamie

[ShanaS]

i have the same question as Heidi, when do u need to change a bulb, when it burns out? or sooner, will you know for sure when your lights are bad? or just go by the 8-12 months and change em?

[evilc66]

What do MH and LEDS offer that other light sources don't?
It's all to do with spectral output and relative intensity. Each light source creates light in a slightly different way. Some light sources can create light more efficiently in some wavelengths better than others. That doesn't mean that any one light source is worse than others. It just means that some lights are more efficient. As long as the lights can provide the corals what they need at the right intensity, then anything can be used. PC's have typically been considered the bottom rung of the lighting ladder, but that's only because manufacturers have been always considered them a cheap, and less critical technology. As a result, the phosphors used have been sub-standard compared to T5, even though they are basically identicle. Companies like Current USA, UVL and Hamilton have been using T5 phosphors in their lamps for a while now, and the difference in output over your standard PCs is considerable. Now, PCs will never be as powerful as T5HO because of the geometry and reflector issues.


Is it their high par, high kelvins?
High PAR only does you good if the light is in the right wavelengths for what you are growing. Obviously, most lights targeted for reef lighting are set up the right way, so more PAR is better. But, there is a trade off with color. If you like deep blue tanks, then you don't always get the option of having super high PAR. For the most part, as long as you don't venture outside of what is considered the norm for reef lighting, it all works.


What does *watts* have to do with coral growth is anything? i.e. 150~250~18~24, ect ect.

Thanks again Evil

Jamie
Watts has very little to do with anything. It used to be a simple metric to use back in the day when PCs were still very popular to guage the relative performance of the fixture over a certain tank. It was the old watts per gallon rule. This all gets back to efficiency. T5HO, MH, and LED all produce more light per watt, so putting the same wattage of light over the same tank now means you are putting more light into the same area. LEDs were really the technology that put the last nail in the coffin for that old rule, as LEDs can produce tons of PAR for very little energy used.

[evilc66]

I wonder about light a lot too. I hope this question is direct enough here goes:
I have a MH 250 pendent it came with a 20,000K lamp.
1.Do any coral need more then this lamp? Is there any color of light I should be adding to this for my corals health? (I am not terribly concerned with the way everything looks just yet, I really want to just grow my coral).
2. My lamp came w/ the fixture so I figure it's elcheapo. How do you know when you need to replace your MH lamp, do they burnout like a normal light bulb, dim, or is it just a timed thing like after 12 months you replace it?

Thanks again for your help!
-Heidi
1. No, not really. The only difference between a lamp like you have and a different brand/color temperature is the amount of PAR it produces, the color of the light, and the average lifespan of the bulb. Typically, cheap bulbs will perform poorly in all three categories. Quality name brand bulbs will always perform better. Now, not all bulbs of the same color temperature perform the same, so some research may be needed to find the best balance. Typically, the Phoenix 14K is a no-brainer, with deep blue coloring (more like 20K), good fluorescence, and long life.

2. Like I mentioned before, cheap bulbs have shorter lifespans. So what does that mean? Well, it doesn't mean that the bulb will burn out after 12 months of use. Typically, there is a spectral shift (changes color), and a drop in intensity. The higher quality the bulb, the longer it will take for that change in performance to happen, and the relative drop in performance will be smaller. The spectral shift can be problematic, depending on how bad it shifts. The major spectral spikes could shift off, and become less effective for coral growth, or could induce unwanted issues like increased algae growth. Most of the time, the worst issue is a loss in intensity. The 12 month cycle for MH is to reduce the shock to the tank once the bulb is replaced. The longer you let it go (and you can let it go quite a while with certain bulbs), the more careful you have to be with acclimation. I've been running a 150W Phoenix 14K for a little over a year with little to no ill effect, but had another Phoenix start creating algae issues at 18 months.

[MizTanks]

Hi Evilc66

Haha gotta another question for you. I just have to pray you understand this one because I'm not even sure how to ask it right.
When it comes to photosynthesis and the corals that totally rely on it, what are we looking for in our lamps to recreate this process? I think you may have touched on this in previous posts but I haven't quit got it yet :) is it a combination of pars and kelvins?

[evilc66]

This is the photosythetic action spectra

http://www.theoremeinnovation.com/images/action%20spectrum%20en.jpg

This is basically shows how effective different wavelengths are at feeding the photosynthetic process. This graph combines chlorophyll A and B. You can find the graphs for each chloropyll online easy enough if you want to break it down further, but this shows what 99% of reefers want to see.

If you want the most ideal light source, recreate this. It's not very practical, and it's not going to look good either. It would be the most efficient use of energy though. The important area that we want to hit is the area between 420nm and 460nm. That's where the bulk of the work is done. The area between 630nm and 680nm is important too, but not quite to the degree that this graph shows. Those are the two peak areas of the visible spectrum where photsynthesis makes the most efficient use of the light.

[CalmSeasQuest]

Thanks for the chart Clive - The 650-680 spike does seem to argue for the inclusion of a "bit" of red, either through red LED or a few warmer whites?