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Discussion Starter · #1 · (Edited)
I suggest using this much more up to date thread, which will be updated as necessary, http://www.plantedtank.net/forums/showthread.php?t=184368 instead of proceeding here.

I have been wondering how much PAR a typical T12 light produces. Like most everyone else I have just assumed that watts per gallon was a way to guess the light from T12 bulbs, but there is no more reason to expect that to mean anything than there is to expect it to mean anything for other bulb types. So, I decided to do some testing.

I borrowed a new two bulb 48 inch T12 light fixture from one of our local aquatic plant club members, bought a new T12 bulb - a Phillips "Natural Sunshine", 40 watt 5000K, 92 CRI bulb at HD, borrowed our club PAR meter and took some readings. Since I have previously found that I get virtually the same readings with water in the tank and with air in the tank, I omitted the water this time. Then I plotted my smoothed data on a common plot with T5 and PC data:



To compare this with "watts per gallon", I know that a couple of 2 bulb T12 fixtures will grow plants in a 55 gallon tank. That tank is 20 inches deep, so if the substrate thickness is about the same as the height of the bulbs above the top of the tank, each bulb should give about 9 micromols of PAR, or 36 micromols for 4 bulbs. That is right in the middle of the low light range. So my data is consistent with real life results.

The light fixture I borrowed has an acrylic splash shield and a removable back, which is a white reflector. I tested the light with and without the splash shield to find that the shield reduces the intensity about 7%. Testing with and without the white "reflector" shows that the reflector increases the intensity by about 36%. The data used for the chart is with both the shield and the reflector.

Some popular tanks are only 12 inches high. For those tanks T12 bulbs should give about 25 micromols per bulb, so a 2 bulb fixture will give low medium light intensity, probably a good choice for many people with one of those tanks.

I believe T8 bulbs produce about the same amount of light as T12 bulbs, but at a lower wattage, because they are more efficient. The fixture I borrowed uses starters and magnetic ballasts, so I didn't try it with a T8 bulb.

EDIT: Updated chart above and added the following chart:
Another way to use this is to convert it into a simple table, that lets you select a lighting option based on tank height, how high you want the light to be above the top of that tank, and how much light you want. This assumes that multiple bulbs are mounted close together, reflectors are typical for that particular type of light. And, I left out the AH Supply light kits.


EDIT (again) New chart added.

The T5HO line on the first chart has been difficult to apply, because so many cheap T5HO lights with less than good reflectors are now available. To make it easier to estimate how much light you can get from different quality T5HO lights, try this chart:

And, to judge the quality of the reflectors:
 

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Discussion Starter · #3 ·
Spiral CF bulbs are a different breed of light. The ones on that chart are all linear tubes which tend to produce the same PAR for any length of bulb, with the length to be used depending only on the length of the tank they are to be used over. But, spiral bulbs have varying lengths twisted together to get all of the light emitted over one small area. There is a thread in the stickies that I think covers those bulbs as well as they can be, for now.

I have enjoyed working with lights since I worked for NASA many years ago, when I was working on a "bulb" that was a water cooled tungsten arc bulb, using argon as the gas flowing through it. Now, that was BRIGHT!
 

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Discussion Starter · #9 ·
I haven't tested T5NO lights, nor have I seen any data from anyone else for them. I do know that T5NO lights are more efficient than T5HO - more light per watt - and T5NO lights are a bit more than half the wattage of T5HO lights. So, a T5NO light should produce more than half the light that a T5HO light does, but only if it has the same quality of single bulb reflector. Unfortunately, I don't think any T5NO light does have the same quality reflector. I think the best guess I can make is that a 2 bulb T5NO light will produce about the same PAR as a typical one bulb T5HO light. I suspect it produces less PAR than that.

And, remember, AH Supply PC light fixtures have uniquely great reflectors. Coralife fixtures, for example, don't have nearly as good reflectors. And, many cheap PC light fixtures effectively have no reflector at all, because they allow no room for one. They might produce only half the PAR as an AH Supply light.
 

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Discussion Starter · #11 ·
So if you had a decent reflector for T-12 what would you guess the increase would be.

Not sure there's a valid reason to use them anymore but having used them for 25 years it's like losing an old friend. lol

SteveU
I think you might gain another 30-40% if you used a somewhat parabolic, highly polished aluminum (MIRO 4) reflector, that was big enough for that size bulb. That would barely be a significant increase.
 

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Discussion Starter · #16 ·
Hoppy, if I reflectorize my little DIY LED fixture and mail it to you, would you mind running it through this same test?
I wouldn't want too accept the responsibility for getting the light back to you in operating condition. Have you looked for an aquatic plants group near you, like http://www.kcfishclub.org/ That might be a group that has a PAR meter, or one of their members may have one.
 

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Discussion Starter · #17 ·
Great information for a planted noob like me. Would you answer a question for me? I plan to step up from a low tech 29 gal to a low tech 55 gal. I'm considering going with either 3x32 watt T-8s or 3x28 watt T-5 NO's. I do plan on doing an occasion excel dose, using eco complete, and low light/hard to kill plants. Would these choices be good lighting for what I want? Suggestions....Thanks in advance.
3 T8 bulbs on a 55 gallon tank, 20 inches high, or 1 T5NO bulb, should give you low light. Or 2 T5NO bulbs should give medium light. Of course if you choose to hang your light above the top of the tank, which I think is the best way to light a tank, you could use even a single T5HO light - hanging 4-5 inches above the top of the tank, to get low medium light. That gives you the best uniformity of light in the tank.
 

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Discussion Starter · #22 ·
So you put one bulb in a two-bulb fixture?

I have two-bulb T12 shop lights, and when I install only one bulb, it lights up very dimly until I pop in the other bulb. Did you ever install a second bulb to see if there was a change in brightness?

I wonder if this could have given you incorrect data...
I didn't try two bulbs because I didn't want to pay for two. But, the bulb lit up as brightly as I usually see, anything but dimly. I don't recall any previous magnetic ballasted T12 fixture I have used doing what you saw, but I don't rule it out. The fixture had two power cords, two switches, so I assumed it was intended to run one bulb alone if desired.
 

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Discussion Starter · #25 ·
I did some experimenting with mylar, aluminum foil, and ordinary white paint as reflectors. To my surprise, the mylar was the least effective, the aluminum foil the most effective, but just barely better than white paint. I didn't use any special white paint, just what I had in a spray can at the time. I believe if you take care to get an ultra white paint you will get better results with that than with aluminum foil, and certainly better than with mylar. The differences I found were around 15-20% from best to worst, so the light doesn't look much different, but a PAR meter shows the differences.
 

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Discussion Starter · #26 · (Edited)
Today, I went back over the data I received from others about various types of bulbs and fixtures, and realized that I could characterize non-AHS PC lights as well as the AHS lights, and that I had one data point for a 150 watt HQI fixture. So, I added that to my chart of PAR vs distance, double checking how I derived that chart. It changed a little, on double checking, but not significantly. Of course the HQI line is just there for comparison, it isn't nearly good enough to use for selecting that type of fixture. The other lines should be good enough to get you into the low, medium or high light categories pretty reliably.


EDIT:
Another way to use this is to convert it into a simple table, that lets you select a lighting option based on tank height, how high you want the light to be above the top of that tank, and how much light you want. This assumes that multiple bulbs are mounted close together, reflectors are typical for that particular type of light. And, I left out the AH Supply light kits.
 

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Discussion Starter · #34 ·
What's the conversion factor from LUX to PAR? I understand it would't be exact because of what PAR and LUX are and that different bulbs perform differently throughout the spectrum. Still, it would be useful information to have a ball-park idea of how the two compare from an average bulb.
I haven't tried to determine the answer to that. Most bulb manufacturers don't print the LUX @ X inches rating on their bulb packages, so I never felt it was an important thing to know. I do know that the conversion factor would be much different for a GE9325K bulb, a 6500K cool white bulb, a 10,000K bulb, etc. How much different I don't know either. Someone else can have the fun of figuring this out:smile:

T5NO lights are interesting. I read a few years ago that the efficiency for converting watts to light for a T5NO bulb is higher than for a T5HO bulb. And, I know that for any given length bulb, T5NO bulbs are a little more than half the wattage of T5HO bulbs. From that you could assume that a 2 bulb fixture with T5NO bulbs would produce about the same or a little more PAR than a one bulb T5HO fixture. Except, that few T5NO fixtures use reflectors that are nearly as good as typical T5HO fixtures. And, the reflector accounts for a big percentage of the efficiency of T5 bulbs. Until someone gets several PAR meter reading for a few different T5NO fixtures I don't know how we will ever know how to judge those fixtures.
 

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Discussion Starter · #38 ·
tom and hoppy where do you think my 192w (2x96w) power compact bulbs stand in the line of par now that they are over 2-20H tanks with the lights beening 18-20 from the substrate, oh and I also have c02 now just need to get the bottle filled and recert.
Those tanks are 24 inches long, right? And, they are end to end, or 48 inches total length? With a pair of 35 inch long lights sitting on the top of the tanks? Assuming that is all correct, the half of each tank directly under the pair of bulbs, which have to be close together, given the 12 inch depth of the tanks, would be about twice what one bulb would give.

The big unknown is whether these are like AH Supply light kits, or like Coralife light fixtures. If like AH Supply, the PAR would be around 100 micromols of PAR, but if like Coralife, it would be more like 40 micromols of PAR. At the end of each tank not directly under the bulbs, the intensity would be quite a bit less.
 

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Discussion Starter · #46 ·
Ok im newer to planted tanks and trying to learn as much as i can as i slowly build up my 75g tanks. Right now i am trying to figgure out my lighting needs. So here is my question with only being able to get t5no lights at 2x28watts how many would i need to buy to put me at the higher end low to low mid mid light range if my substrate will be at about 20 to 22in from my light with basic reflection ie white paint as the min but more likly Aluminium coil stock lind custom hood. I know that i should try for a better light scorce but because of where i live and cash flow it has limited me in what i can buy at this time.
That is actually a difficult question to answer. Those charts for T5 are based on the light you get with typical T5 highly polished aluminum reflectors. You can make a lot of assumptions about what percentage of the light comes from reflection off the really good reflectors, and use that to guess at how much PAR you would get without any reflector, then add maybe 10-20% more for the white painted, but flat reflective surface. What you would end up with would be very inaccurate, and probably worthless.

Or, since 28 watt T5NO bulbs are about 48 inches long, you can assume they produce the same light as a T8 48 inch bulb, but use less electricity to do so. That is probably a better guess. Then I would assume they produce perhaps 20% more light than that due to the smaller tube size, giving what should be a brighter light. Doing that, my guess is that 2-28 watt T5NO bulbs at 20 -22 inches with a flat white reflector would give you low light, just barely within the range for low light. Using aluminum foil instead of white paint would slightly increase the amount of light, because white paint is a very good reflector surface, almost as good as aluminum foil. But, it would be worth doing since it might be enough improvement to get the light intensity well within the low light range.

You could further improve this by using a curved reflector surface that surrounds the tubes on 3 sides - like a section of rain gutter, for example. Then line that with aluminum foil. I doubt that this would get you to medium light, but it might.
 

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Discussion Starter · #55 ·
I found this thread to be very helpful--and money saving! Now I know that I only need 2x54w T5HO bulbs for my 75g to be the high light tank I want. :biggrin:

Do you think it's just a marketing ploy to make the 4, 6, or 8 bulb T5HO fixtures?

-Lisa
T5HO fixtures are usually made for reef tanks, where a lot more light is used. That market is a lot bigger than the planted tank market, too. So, manufacturers make lights that are appropriate for reef tanks, with multiple bulbs, actinic bulbs, 12000K color temperature bulbs, etc. Only occasionally do you see fixtures made just for planted tanks, and they almost always have only 2 bulbs.
 

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Discussion Starter · #60 ·
Hi Hoppy,

Not sure if you missed my question?

Was wondering how LEDs compare with the other lights you mention?

In particular, TMC GroBeams?

Many thanks :icon_smil
Sorry, I just forgot to come back to it.

LEDs aren't like other lights. For one thing a single LED doesn't produce enough light to work on any but the small nano tanks. So, you always need to use an array of LEDs to do a good job lighting a planted tank. For the moment, this, http://www.plantedtank.net/forums/diy/84212-designing-building-led-fixture-22.html#post1102937 is the best I can come up with for picking LED lights. And, so far I haven't seen an LED light fixture that I think is a good planted tank light, so to use LEDs you have to DIY one.

That GroBeam 1000 version is only about 8 inches square, so it is probably only effective on a 12 inch maximum depth (front to back) tank, and a 55 gallon tank, for example would need about 5 of them. I don't know what they cost, but I suspect 5 of them would empty most of our hobby budgets. Price has always been the problem with LED fixtures.
 

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Discussion Starter · #62 ·
I only looked at the panel light variety instead of the strips, because I fell very strongly that LEDs should be used in an array that covers most of the top of the tank. If you use strips of LEDs they should be close enough together so you effectively have a panel of LEDs. (Just my opinion.)
 

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Discussion Starter · #65 ·
So from the info on the chart my dual 17W T8 isn't really supplying any sufficent light to my plants. It sits about 17" from the substrate level is this correct ?
It might barely give enough light for Anubias, ferns and mosses. Those are good lights for a typical 12 inch high tank.
 

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Discussion Starter · #68 ·
I beginning to think that the LFS owner, when he said it was enough, was bs-ing me.

I have a 20G tall (or high) that is approximately 18 inches tall. I have a Jebo 24" fixture with two power compact 24W bulbs. The two options I have to mount it would raise the bottom of the light fixture anywhere from 3 to 6 inches off the top of the water.

Will this do for HC, Dwarf Riccia and Java Moss?
I don't know of any 24 watt PC bulbs, other than UV bulbs. Are you sure they aren't 65 watt bulbs?
 
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