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Old 08-28-2011, 08:16 PM   #1 (permalink)
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Default Aquarium Lighting Calculator (1st Draft)

I have recently started my first planted aquarium (NPT), and built my own stand and hood. In the process I have been doing a ton of online research to figure out how much light I need and which bulbs to use. My DIY hood has screw-in sockets, limiting my options.

After learning of all of the uncertainties of Watts/Gallon estimates as well more than I cared to know about lumens, lux, par, pur and photosynthesis I came up with the attached Excel calculator. It uses Lumens/Watt figures that can be found for most bulbs along with tank dimensions to calculate LUX at a given depth. That can be compared to a table of LUX ranges ranging from "Very Low" to "Very High" light levels (this is the least certain part of it, and the one I'm most interested to get feedback on) I know that Lumens/Lux refer to the visible spectrum of light that doesn't correspond to the photosynthetic range...but I am not going to be purchasing a PAR meter anytime in the near future.

I have read many threads on this subject, and can find no other quick calculation that will put you in the ballpark of lighting requirements. I have also seen that the "standard" bulb people use for the watts per gallon estimates varies greatly. Some say the T-12 is the standard (~60 Lum/Watt), while the oft-referred to Rex Griggs LSI method appears to use T-5 as the standard (~90 Lum/Watt).

This is meant to very quickly get someone in the ballpark of meeting their lighting requirements. I would be very much interested to hear from experienced people as to how this calculator's results compare to their experience.

Thanks for any input, and I hope this ultimately helps someone.
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File Type: xls Aquarium Light Calculator 1.1.xls (23.0 KB, 4599 views)
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Old 08-29-2011, 10:42 AM   #2 (permalink)
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Default Re: Aquarium Lighting Calculator (1st Draft)

Very interesting! In the bulb type--lumens/watt chart, it gives two values for T5: 88 and 98.4. I assume that this is the difference between NO and HO. Is this correct?

I'm glad you included this, because the lumens/watt value was not given anywhere on my recently purchased Coralife 6700K NO tubes. (Yet another reason I dislike Coralife!)

Using the 88 figure, I calculate a Lux @ depth value for my 40 gal. breeder to be 6,398, at the low end of the very low light category. Intuitively, this seems to be an underestimate of my light levels, since I am getting good compact growth from medium light genera such as Bacopa, Nymphaea, and Saggitaria.

This is not meant to discourage you--quite the opposite! With some tweaking and testing, this could be a very valuable tool. As you point out, it won't replace a PAR meter, but it could eliminate some of the guesswork in choosing a light fixture.

--Michael
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Old 08-29-2011, 08:57 PM   #3 (permalink)
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I don't mean to sound like a downer but its completly pointless to figure lux and lumens per watt because its only what your eyes see. It has nothing to do with growing plants so if you like what a certain light looks like on your tank then I would say your more than in the ballpark for those figures if you know what I mean.
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Old 08-30-2011, 03:16 AM   #4 (permalink)
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Default Re: Aquarium Lighting Calculator (1st Draft)

Michael, as I'm sure you know all of those types of lights have a range of outputs. I tried to find the most typical values for those who couldn't find lumens/watt for their particular bulbs. On the T5 I just put that range because I couldn't decide what figure was more "typical". I don't know what would be appropriate for your bulbs, but I would guess 88 as well.

Would you mind posting your tank dimensions and what you would consider your light levels to be (low, medium?)? This is exactly the feedback I want to try to tweak the calculator.


dstrong, I realize that PAR & lumens/lux don't correlate really well. But they are related...for a particular bulb, when wattage goes up, lumens goes up, and PAR goes up. The relationships are indirect and vary significantly between bulbs, but most bulbs will grow plants, and the more light that comes out, the more they will grow.

People have been getting by with watts per gallon for many years. It is extremely problematic, but not entirely useless. I am hoping this lux approach, while still being problematic, will be even more useful for those without a PAR meter who just want to hit a target light range without doing a master's thesis on lighting.

I'm hoping that I can get enough people to post tank dimensions, bulbs and their thoughts on their light levels that we can verify whether or not this thing actually produces usefull results.
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Old 08-30-2011, 08:41 AM   #5 (permalink)
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I see what your saying I just wanted everyone to keep in mind that there are bulbs on the market listed with outroarously high LUX that have very crappy PAR so everyone should really try and get a PAR rating or at least a spectral graph before they buy any lighting product. If the entire industry demanded it I think the information would be much more readily available and accurate. I do think this is incredably more useful than W/G though.
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Old 08-30-2011, 08:45 AM   #6 (permalink)
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Default Re: Aquarium Lighting Calculator (1st Draft)

Happy to! This is a standard 40 gallon breeder, 18" x 36" x 17" tall. The light fixture is suspended about 4" above the rim of the tank. The fixture is actually 48", and extends about 6" on either side of the tank. It is the old Coralife two tube T5 NO slim profile fixture with their bad mylar reflector. I try to use 6700K tubes with good output in the red and blue wave lengths, but these are becoming very difficult to find. Coralife still sells them, but they are expensive and only last about 5 months! (Ask me why I dislike Coralife.)

Using Hoppy's light intensity chart, this should give me medium light. And my subjective impression is that this is correct.

Mick, what I hope this calculator will do is act as a guide to help new hobbyists and people who do not have access to a PAR meter. People should be cautioned that it is valid only for full-spectrum lighting that has good output in the red and blue wave lengths, as well as the yellow and green part of the spectrum that our eyes are most sensitive to. In a perfect world we would all have PAR meters, but as the ancient Greeks said, sometimes the perfect is the enemy of the good.

P.S. Mick, I was writing this as your last post went up. I think we are all on the same page.
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Old 08-30-2011, 10:43 AM   #7 (permalink)
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Default Re: Aquarium Lighting Calculator (1st Draft)

Ideally all bulbs would have a full spectral profile and PAR data. It would be great if we could put together a database/table of bulbs with that info in the meantime.

No doubt that there is a lot more to lighting. My frustration has been with smply figuring out how to get started with some certainty. I was shooting for a minimum lighting threshold that would grow many plants within the Walstad NPT approach.

It shouldn't be that hard to find that kind of basic information. I've read a dozen threads that just result in a general impression that no one can possibly know anything about lighting without a $150 PAR meter. That is just silly and overly academic.

If you read this post, please contribute your tank dimension, bulb info & lighting level thoughts.

Thanks a lot!
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Old 08-30-2011, 01:33 PM   #8 (permalink)
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Default Re: Aquarium Lighting Calculator (1st Draft)

I appreciate your effort, but IMO these light charts and/or calculators simply don't work. There are too many different types of bulbs, manufacturers, setups, plants, goals, lifestyles, etc to calculate in for this too be very useful.

Even within a certain bulb type. Let's say T5HO. There is a wide variance of light intensity that one light with the same size bulbs would give off. Sometimes the differences have been 2, even 3x par. Also many run an afternoon burst (doubling of their light) to satisfy certain plants. Is it high-light even if I run the burst for only 1 or 2 hours. See where I'm going. The beauty of the forum is you get to see so many different types of setups in the 'real world' and can make a better decision on that type of info IMO than you can from a chart/calculator.
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Old 08-30-2011, 02:08 PM   #9 (permalink)
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Default Re: Aquarium Lighting Calculator (1st Draft)

House of Cards, those of us with sophisticated lighting set-ups using complex variable photoperiods are not the intended users of this calculator. And of course any results one gets from the calculator should be tested against actual experience.

Please offer suggestions to make it work better.

--Michael
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Old 08-30-2011, 02:14 PM   #10 (permalink)
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Default Re: Aquarium Lighting Calculator (1st Draft)

Quote:
Originally Posted by Michael View Post
House of Cards, those of us with sophisticated lighting set-ups using complex variable photoperiods are not the intended users of this calculator. And of course any results one gets from the calculator should be tested against actual experience.

Please offer suggestions to make it work better.

--Michael
Michael, that's my honest opinion. I don't thing they work, period. I don't think having an afternoon burst is a sophisticated lighting system. Even if we put that aside, the intensity of lights within each type vary too much by manufacturer making input impossible. Am I not allowed to state an honest response. Again the beauty of the forum is you can view many different setups that might be closer to what you have.
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