[brokefoot]

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.

 

[Michael]

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

 

[dstrong]

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.

 

[brokefoot]

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.

 

[dstrong]

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.

 

[Michael]

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.

****, 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. ****, I was writing this as your last post went up. I think we are all on the same page.

 

[brokefoot]

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!

 

[houseofcards]

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.

 

[Michael]

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

 

[houseofcards]

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.

 

[Michael]

Of course you are allowed to give an honest response, no one said otherwise.

The calculator allows you to enter a value for lumens per watt. This information should be available from the manufacturer (except Coralife). Therefore, there is some correction built in for variance among the same type of lamp from different manufacturers. This is one of the reasons I think this calculator has a chance of being more useful than other ways of estimating light intensity over aquaria.

 

[wet]

Hey brokefoot. I agree with the points that these models can only scale so far, but your use of Lumens/Sq. Inch (LSI) and stuff is very similar to the stuff Wizard~Of~Ozz and I came up with on AquariumAdvice.com in 2006 (these are still stickies there):
http://www.aquariumadvice.com/forums/f24/updating-the-wpg-rule-theory-69964.html
http://www.aquariumadvice.com/forums/f24/survey-for-updating-the-wpg-rule-theory-70271.html

Kind of a bummer to see our metric here without credit to Ozz, despite our metric's faults. You may dig this though: Plantbrain's diss of the method, our response, and my correlating that data vs FitchFamily's great work comparing Amano's tanks: http://www.aquariumadvice.com/forums/f24/updating-the-wpg-rule-theory-69964-11.html

(We had the idea of standardizing back to "Equivalent T12 WPG" for various bulb types after regressing data from AquaBotanic's old collection of the data, different manufacturer ratings for lumens, and a survey of the AA community to build our lighting thresholds. This was shortsighted.)

You'll also find the thread has a few plain text versions of our informal survey to determine lighting thresholds.

All that said, much better to devote your effort to automating/building a calculator for Hoppy's stuff in my opinion. He has made strides with PAR and quantifying light, has a growing sample size, has already attempted to tackle emerging technology (LEDs for the aquarium), and probably explains it all better than anyone.

http://www.plantedtank.net/forums/lighting/105774-par-vs-distance-t5-t12-pc.html

I think that metric has much more potential than LUX. There is a reason LUX never caught on.

 

[Michael]

Great comments, Wet. Hoppy's charts are the only sensible guide to lighting that I have found. Thanks for the other links, I'll do some digging myself.

 

[brokefoot]

Wet,

Wow...I wish I had found that thread earlier. I have a lot of reading to do. Also, thanks for the link to Hoppy's thread.

I was not able to get the links to work to actually see Ozz's paper or calculator. Is it still available somewhere online? By the way, I would certainly have credited Ozz had I seen his thread. I got the math for the calculator from some other thread on another forum that I can't seem to find again.

I have not read all of that thread on Hoppy's charts, but will try to go through it tomorrow.

Maybe I'll need to change directions on my calculations. I went with Lux as opposed to PAR just because I found a way to estimate it.

But I still would like to have a calculator that would help someone (including me) quickly figure out how to meet their lighting needs without having to read 50 pages of forum threads. Does such a thing exist that is readily available? Maybe I just haven't found it. Obviously people have spent a lot of time and effort looking into this topic. I don't want to re-invent the wheel.

Thanks again for all the feedback and links!

 

[dstrong]

Maybe I'm thinking to simply but why don't people request PAR info and spectral graphs from the manufacturer if its not on the packaging? I can't afford a PAR meter and that's how I figure my lighting needs, I just won't buy anything that's supposed to grow plants if the manufacturer can't even supply that information, and if I have that information I don't need to figure anything because I know what I have. I don't mean to downplay the work you guys put in, I think its great, but I'm just spitballin.

 

[brokefoot]

dstrong, good point. My thinking is just that it would make life easier if that PAR/spectral data were gathered together in one place for many common bulbs.

It would also save some of us lighting newbies lots of trial/error (read money/time) going through multiple bulb configurations.

 

[dstrong]

True I'll see if I can find the PAR info I used to have for my bulbs

 

[houseofcards]

dstrong, good point. My thinking is just that it would make life easier if that PAR/spectral data were gathered together in one place for many common bulbs.

It would also save some of us lighting newbies lots of trial/error (read money/time) going through multiple bulb configurations.

This is why it's tough to categorize these things into nice, neat buckets. The PAR values change dramatically based on reflector design. The same bulbs can seemingly have different PARs, in fact the PAR values can be so different that one might have low light and another medium/high light with the same bulbs but a different reflector. This has been discussed in hoppy's chart. A lot of the data is based on one light manufacturer which was not even reflective (no pun) of the market in general. In addition, additives like co2, water clarity, etc. will also play a role in how well a bulb performs. I'm not trying to be negative, just realistic in what constitutes lighting levels in one's tank.

 

[dstrong]

Well you obviously can't know how much PAR is reaching the bottom of your tank without a meter but I think it would be awesome to have a growing database of PAR information so I don't have to contact the manufacturer every time I want to try a new bulb that has crappy specs on the packaging. Its a given that the PAR will be different with different reflectors and distances but if you know the bulb its easy for any sensable human being to maximize its usefullness without knowing the specific numbers hitting the substrate.

 

[dstrong]

Crap I didn't save the emails. =/ I had a bunch of PAR info for CFLs and some T5s that you could buy cheap at Home Depot ect.....