# A Light Calculation Chart



## essabee

I have created simple “Light Calculation Chart” using simple formulas in MS Excel (I am no computer buff) which might be helpful to fledgling planted tank hobbyist. I wish to share the same with you all. 

I have divided the light intensities into 5 categories taking the Lumen per Square Inch (LSI) at the middle depth of the tank. These categories are:- 

1. Low Lit – The light will only be sufficient for slow growing low light plants like anubias, java fern, and moss. 

2. Medium Lit – The light is sufficient for growing common undemanding aquatic plants. 

3. Well Lit – The light is good for all except the difficult demanding aquatic plants. CO2 is not a must in this category but you will find good response if you use it. 

4. Bright Lit – CO2 becomes a must and you are free to grow whatever you fancy. 

5. Very High Lit – Sky is the limit here as long you don’t evaporate your tank. CO2, Fertilisers and frequent trimming of the plants will enslave you in this category. 

I have done away with the ancient Watts per Gallon regime but only for the sake of old times will show it in the results.

Download this chart and save it before using it:

https://spreadsheets.google.com/ccc?key=0AswmPrhGQOnKdDdIR3pIc1lQTmVqb3NRLVFvVDI0ZFE&hl=en

In the tank Volume just type in the white spaces the Length, Height, and Width in inches of the tank you want to find out about. Make sure that the measurement of height is the mean height of water column above the substrate. (if you have the measurement in cm then you can find out the same in inches using the conversion table) 

In the total lumen installed chart just type in the white spaces the total wattage used against the type of bulb on the left. 

In the reflector chart just choose the type of reflector used by typing 1 in the white space on the right of the reflector type. 

Now just scroll down and see the result against the Unknown tank. 

You can use the chart to find out about your present tank or plan for your future tank.


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## Hoppy

I can't get the link to work. Google says it isn't a valid spreadsheet URL. I have no idea how to fix that.


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## StillLearning

Think this is the one suppose to be posted. I was reading the other post they were talking in earlier and it was there.


http://spreadsheets.google.com/ccc?key=0Aoveq6RSOtVtdGV3VXFuTWZBMG53OTZPY3Y0cHFHbWc&hl=en


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## essabee

StillLearning said:


> Think this is the one suppose to be posted. I was reading the other post they were talking in earlier and it was there.
> 
> 
> http://spreadsheets.google.com/ccc?key=0Aoveq6RSOtVtdGV3VXFuTWZBMG53OTZPY3Y0cHFHbWc&hl=en



Yes that is the correct link. Thank you.

I have edited my post.


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## wkndracer

interesting, thanks for postig.


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## JMH1998

So I calculated mine to be a 3 low lit, which I expected and it is only anubias that I really have (plan on getting Java Ferns soon) so I guess that is all fine. My question with this situation is will that be enough to get them to pearl? I have been looking everyday and nothing so far and not sure if they will in that condition.


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## tuonor

Nice work. 

Not sure if I'm downloading the right version but noticed that cells H22 and I22 seem to be hard coded (and seems like they should link to C6 and G17 respectively). Some of the lumen produced cells also have similar issues. 

Easy enought to fix if you download it to excel, but this might be throwing results off in the version that was posted.


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## Hoppy

In case anyone else has the difficulty I had, you can download this as an Excel spreadsheet by clicking the "file" tab at the upper left and selecting that option. I haven't tried using this yet, but I will.


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## illumnae

The file seems to have been changed from yesterday. Alot of the formulas have been changed to static values, so it doesn't work for me anymore. 

E.g. volume of tank was change from a formula to a static value, calculations for various lumens of light has been removed too


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## newday3000

I justed downloaded and it works fine for me in Excel 2007. Nice tool. This should help many figure out lighting more easily. I vote for a sticky.


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## smp

I'm using Excel 2003. Doesn't work for me at all. Won't even calculate the tank capacity correctly. Most items are "static" values.


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## essabee

I edited the link again. If you don't download and save the chart before use then it gets edited by you and errors creep in. I just do not know how to keep it saved and hope the administrators would help here.


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## StillLearning

essabee im wondering if saving it from your end then attaching it in a zip file here so others may download this way nothing goes wrong would work better.


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## Hoppy

StillLearning said:


> essabee im wondering if saving it from your end then attaching it in a zip file here so others may download this way nothing goes wrong would work better.


But, how do you do this? I looked around the site and I can't see where a document file can be saved on this site.


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## kid creole

essabee said:


> I edited the link again. If you don't download and save the chart before use then it gets edited by you and errors creep in. I just do not know how to keep it saved and hope the administrators would help here.


I tried to edit it online and I couldn't. I could only edit it by downloading and using excel.


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## StillLearning

Hoppy I should of been a little more clear I was just waking up :icon_redf. I ment for essabee to save his original copy to a zip folder and then upload it on plantedtank in a zip folder this way no one can ruin it or edit it and there is always a backup copy. Then what you could do is upload it to google documents or what ever you may use to open the file.

I was thinking maybe it could be coded to html or php this way only the fields can be changed that are ment to be and not any of the ones that shouldnt be. :thumbsup:


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## S&KGray

*Saved as Excel workbook (97-2003 and 2007) and zipped, attached here*

Here you go peeps:

View attachment Light Calculation Chart.zip


Edit: Darn I noticed now that in the Excel files I saved and downloaded, some of the formulas were overwritten with static values as smp noted earlier.

Edit2: Fixed with download from link in essabee's first post. Should be good to go now. I protected the sheet except for the cells where u need to enter data.


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## essabee

S&KGray said:


> Here you go peeps:
> 
> View attachment 18033
> 
> 
> Edit: Darn I noticed now that in the Excel files I saved and downloaded, some of the formulas were overwritten with static values as smp noted earlier.
> 
> Edit2: Fixed with download from link in essabee's first post. Should be good to go now. I protected the sheet except for the cells where u need to enter data.


Thank you. You saved me from correcting my link again and again.


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## itrack4u

I downloaded the file but can't enter any of my numbers. I am not familiar with Excel. Any suggestions please?


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## Hoppy

Next thing is to see if the calculations are consistent with what I think they should show. My first attempt to use it I wasn't paying close enough attention, so I need to start over.


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## smp

Got the zip, and working much better.

Have a question,

What's the difference between "T5 Florescent" and "T5 HO Florescent"

I have 3x54 T5 HO.

When I fill in "G7" with 162 I get 16200 lums
When I fill in "G11" with 162 I get 14418 lums


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## archer772

OK I am a little confused but that doesnt take much much going from Reef to Planted. I also wonder why T-5 Flouresent has higher lumens than T-5 HO and I dont see anything for the T-5 Parabolic Reflectors like Ice Cap and Teks. I am trying to not compare FW Planted to Reefs but thats where I learned lighting.


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## essabee

The normal T5 is more efficient in converting watts into lumen than the T5 HO. What you actually do when choosing a T5 HO is that you pack more power into the same space. That is to say that for the same physical size of bulb - a T5 HO will have a much higher wattage.


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## smp

Do all T5 HO's of the same wattage produce the same lums?


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## fishyjoe24

windows extractor opened it up and unziped it, but I'm having problems typing in numbers. it won't let me type in the numbers.


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## Noxtreme

to bad it doesn't really work for a corner tank


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## JDowns

smp said:


> Do all T5 HO's of the same wattage produce the same lums?


They may have a manufacturer's claimed lumens, but in no way do they put out the same amount of PAR.

I'll give you an example. From a FishNeedIt two bulb fixture. Just by replacing the bulbs that come with the fixture with Geisseman bulbs resulted in a 25% gain in measured PAR. Ask yourself this. Do you honestly think all bulbs are created equal?

Now also by changing the angle of deflection of the reflectors resulted in another 30% gain.

So just by replacing the bulbs and making a minor adjustment in the reflectors results in 50+% gain in PAR.

Food for thought. Say we take four fixtures identical in 4x54w bulbs from four different manufacturers. Tek, FishNeedIt, Catalina, and Corallife. Now lets assume for the sake of arguement the same reflector material (not design). Do you honestly think all four fixtures will produce the same amount of light out of the box? Now lets put the same bulbs from the same manufacturer in each fixture and make them quasi-equal. Do you honestly think all four fixtures will have the same measured PAR output? I have measured them, and can tell you, little things like reflector design (not material), bulbs used, and active cooling are going to greatly effect the amount of light that reaches into the tank. And for the top example in the magnitude of nearly double the light.


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## Hoppy

Lumens are a measure of light as perceived by human eyes, not as perceived by plants. Human eyes are not very sensitive to light at either the red or the blue-violet ends of the spectrum. Plants are more sensitive to light at the ends of the spectrum and less sensitive to light in the middle - yellow/green. That's why using lumens to rate bulbs for plant use isn't a good idea, and it is why PAR is used instead.

Most bulbs are made to please human eyes, so you can expect them to produce more light in the yellow-green area of the spectrum, where our eyes work the best, than at the ends of the spectrum where our eyes are not so sensitive. If you look at spectra charts for typical fluorescent bulbs you will almost always see a big peak in the yellow-green area, but smaller peaks, if any, in the red and blue areas.

Based on that, I think it is very possible that all T5HO bulbs of one length designed for lighting work areas, homes, businesses, etc. will produce about the same lumen output, but it would just be a coincidence if they produced the same PAR.

It is difficult at best to figure out how much light you will get for any specific light fixture and bulb, so any effort to do so will result in a pretty big margin for error. That's why I see no reason to even consider what specific bulb is being used, or what specific reflector. I think it is better to just assume all single tube reflectors are sufficiently alike that we can ignore the differences, and all T5HO bulbs that would be used on a planted tank are sufficiently alike that we can ignore those differences too. And, getting into ballast designs and cooling methods would be unlikely to be beneficial.

The advantage of suspending the light above the tank so it can be raised and lowered is that you can afford to be in error by 50% on guessing the light intensity, because it is so easy to then adjust the intensity by adjusting the height of the fixture above the tank. Ultimately you can only know what the intensity is by measuring it with a PAR meter.

One other factor: if the light is sitting on top of the tank, the intensity near the water line will always be much, much greater than at the substrate. So, no tank with the light on top of the tank can ever be characterized by a single value of the intensity, making trying to be accurate with a guess as to that intensity an impossible goal. But, if the light is suspended a few inches above the top of the tank, that guess becomes much more meaningful, since the variation from water line to substrate is a great deal less.


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## trido

I realize that this is several month old but.... Am I the only one who had problems with the reflector values changing? 
Unless I physically change the value myself, the formula always calculates it with 55%, or no reflector.


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## plantbrain

I've seen charts and watt/lumen spreadsheets for over a decade.

I've never seen one that really offered anything much more than estimative guess at best.

If you take a comparative approach using a real PAR meter, test in a real planted tank, with a real plant, with real water, with real Bulbs in a real aquarium hood........now you can compare the data.

We also know, we do not need to guess, that plants are much better able to use the light much more efficiently at lower PAR when the CO2 is non limiting.
So that is a dependent factor in any such rule of thumb for light, and not discussing that leads to errors. While some plants are called low light plants, most all aquatics are low light plants by definition.

Without careful testing with nutrients/CO2 as independent factors,m we cannot say much and without actually testing the plants with a light meter, it's tough to say much.

Most of these universal charts are not much better than old watt/gal rules IME/IMO and have not led to much insight for planted tanks. The PAR light meter has rather quickly & decisively. It's also much easier to use than the spreadsheets. I understand why folks put these up and want to help, but they really do not help much. It's not just this one etc, it's all the folks that post the light charts etc.

PAR meter cost a bit, but can be shared amongst several folks, resold after the testing you are interested has been done etc.

If you want to discuss each individual unique aspect of each aquarium.........then test the light in PAR. Accounts for all these different variables and the more assumptions and variables we estimate, the more error we introduce.

Some PAR- PUR conversion for specific bulbs might be done I suppose.
I don;'t know, I just have never been convince any of these light charts ever did a lot of good.

They did not predict the ADA light values, not even close.
They do not predict my own tanks, nor those of many others.
Once I tested with the PAR meter, then it all made a lot more sense.

I would had never seen this using these charts however.
You can then check to see if the chart model works in the real world and not just on your own tanks, but more broadly and generally.

You need some verification that the model works, some way to measure and test it.

regards, 
Tom Barr


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## plantbrain

Here's an example of CO2 "stress" and the effects of light:










You might need more light and think that the CO2 is fine or that there's no stress occurring. How do you check that?

Regards, 
Tom Barr


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## trido

plantbrain said:


> not much more than estimative guess at best.


But wouldnt you agree, that's all that is necessary to get a newb somewhere to start from? This spreadsheet for example, gives me the ability to do the math to realize that I have high light over the center of my tank and med on the ends. The two LFS's I have been frequenting both told me that I have very low light because they arent familiar with HO T-5's.
If I were to use the watt per gallon rule, at 4 watts per gallon on my 210G tank I would need 840 watts of light, bascially the three 250 watt MH's and a pair of HO T-5's that I grew the highest light demanding corals with.

The point I make, its not scientific or completely accurate, but better than the advice I got from my local "experts" and far better than just guessing.


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## Simmo2302

i noticed your volume measurement is based on an empty tank. shouldnt you work on the estimated volume of the tank after substrate is put in.

eg. i have a 10 gal tank when empty, but after substrate is put in, the actual water volume is down to 8 gal. wouldnt this mean i have more light intensity in the same space considering there is less water.


also my tank is 11 inches high, down the bottom its says height after substrate is 11 inches. is that because the ideal height for the light is the height of the tank above the substrate.


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## trido

> Make sure that the measurement of height is the mean height of water column above the substrate.


My tank is 29 inches deep. since I have three inches of substrate, I would enter 26. It explains this in the first post.


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## Hoppy

Simmo2302 said:


> i noticed your volume measurement is based on an empty tank. shouldnt you work on the estimated volume of the tank after substrate is put in.
> 
> eg. i have a 10 gal tank when empty, but after substrate is put in, the actual water volume is down to 8 gal. wouldnt this mean i have more light intensity in the same space considering there is less water.


Light is not like fertilizer - it doesn't mix with the volume of water in the tank. It just shines on whatever is in the tank. In fact the water has such a small effect on the light that you can ignore it, and just look at how far the light is from the point where you want to know the intensity. Wattage is also irrelevant, because the types of lighting normally used for aquariums emits a nearly standard amount of light per inch of tube. So a short T5HO bulb gives about the same intensity under it as a long T5HO bulb. The long bulb just lights up more of the tank length. And, a 100 watts of T5 light, for example can give low light or high light on any given tank, depending on how high you hang it above that tank. (Just don't submerge it in the water:icon_lol


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## farmhand

Hoppy said:


> The advantage of suspending the light above the tank so it can be raised and lowered is that you can afford to be in error by 50% on guessing the light intensity, because it is so easy to then adjust the intensity by adjusting the height of the fixture above the tank. Ultimately you can only know what the intensity is by measuring it with a PAR meter.
> 
> One other factor: if the light is sitting on top of the tank, the intensity near the water line will always be much, much greater than at the substrate. So, no tank with the light on top of the tank can ever be characterized by a single value of the intensity, making trying to be accurate with a guess as to that intensity an impossible goal. But, if the light is suspended a few inches above the top of the tank, that guess becomes much more meaningful, since the variation from water line to substrate is a great deal less.


Please excuse if this question is a little off topic. Based on the above quote, when setting up a new tank and unsure of the light needed, would it be better to overkill on the high side of lighting and plan on raising the height to get the desired results?


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## trido

farmhand said:


> Please excuse if this question is a little off topic. Based on the above quote, when setting up a new tank and unsure of the light needed, would it be better to overkill on the high side of lighting and plan on raising the height to get the desired results?


 
IMO, yes. If you over kill now and can raise the lights then you are far better off than if you buy too little and then have to eat the cost of buying a second lighting set up because your are wanting more.


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## Hoppy

farmhand said:


> Please excuse if this question is a little off topic. Based on the above quote, when setting up a new tank and unsure of the light needed, would it be better to overkill on the high side of lighting and plan on raising the height to get the desired results?


I think the "best" way to light a planted tank is to use the tank without a glass top, hang the light several inches above the top of the tank, so it is easy to reach into the tank to do daily minor maintenance. That reduces the light intensity from what it would be if the light was sitting on top of the tank. So, I think yes, it is better to get more light than you need and hang the light high enough to reduce it to what you need.

If you want a hood over the tank, made to match the tank stand, and cover the entire top of the tank, then of course you can't hang the light several inches over the tank easily, and you can't adjust the intensity by raising or lowering the light. For that case, it is best to buy a light that gives no more light than you need for the type of planted tank you want to have.


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## plantbrain

trido said:


> But wouldnt you agree, that's all that is necessary to get a newb somewhere to start from? This spreadsheet for example, gives me the ability to do the math to realize that I have high light over the center of my tank and med on the ends. The two LFS's I have been frequenting both told me that I have very low light because they arent familiar with HO T-5's.
> If I were to use the watt per gallon rule, at 4 watts per gallon on my 210G tank I would need 840 watts of light, bascially the three 250 watt MH's and a pair of HO T-5's that I grew the highest light demanding corals with.
> 
> The point I make, its not scientific or completely accurate, but better than the advice I got from my local "experts" and far better than just guessing.


I think it is simply better for the newbie to ask and have folks they ask, to know based on experience, or have a PAR meter.

Otherwise, a simple W/gal gal rule + *some additions for different light types*(say T12 vs PC vs T5) is just as good and lots easier to use.

You are not really going to ever improve upon this muck otherwise.
If you want more accuracy, get a PAR meter, measure it etc, and estimate it based on experience.

You can only go so far with spreadsheets and different converting factors, etc.

Folks often tell newbies to buy a test kit to measure NO3.
Why not a light meter? Why don't more folks have one? LFS's?
Rent them etc.

I see lots of wasted time getting nowhere with this and not just this example, but the dozens or so I've seen over the last decade or so.

None have been any significant improvement.

Corals have other issues, folks do not know the Light compensation points or have enough controls over the other aspects of growth/culture to get at many of those numbers, we do for plants however.

Regards, 
Tom Barr


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## plantbrain

Hoppy said:


> I think the "best" way to light a planted tank is to use the tank without a glass top, hang the light several inches above the top of the tank, so it is easy to reach into the tank to do daily minor maintenance. That reduces the light intensity from what it would be if the light was sitting on top of the tank. So, I think yes, it is better to get more light than you need and hang the light high enough to reduce it to what you need.
> 
> If you want a hood over the tank, made to match the tank stand, and cover the entire top of the tank, then of course you can't hang the light several inches over the tank easily, and you can't adjust the intensity by raising or lowering the light. For that case, it is best to buy a light that gives no more light than you need for the type of planted tank you want to have.


The other option is to have several bulbs with separate plugs for each.
This way you can turn on each set of bulbs to achieve whatever intensity you desire and not need to raise or lower the lighting, this maximizes the efficiency and spread without losing light intensity to the Inverse square law.

Say you want min light: 2 bulbs, wide apart
Med light: 3bulbs, high light : 4 bulbs etc.

You can also use the 3-4 bulb array with 1hour noon blast, and scale these up to the full time frames each or in series, so the amount of light added can be over a wide variable range.

Still, a simple PAR meter, a LFS rental etc(good way to make some $$$ for them) would answer any of these variables easily.

Depth, volume of the tank, sq ft, water, particular plants, shorter foreground plant, inter and intra specific shading effects, any ballast differences, bulb brand differences, reflector issues, glass tops, tannins in the water, type of lighting on and on and on..........

The light curves are non linear, so they'd need some log transformation to adjust for a spreadsheet, so simple scaling does not work well.

Regards, 
Tom Barr


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## ajirsult

Great article. I was reading about how lumens matter and watts is just the power usage of the bulb. great to see your work using lumens for deciding the lighting for a planted aquarium. Could you recommend any reading material about planted aquarium?


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## 20cc

no led option :frown2:


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