# watts per gallon sucks! rating light effectiveness using a new metric?



## OverStocked (May 26, 2007)

The real problem is there is no set metric to judge lights. It is very dependent on so many things making any rule to use is pointless.


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## Dave-H (Jul 29, 2010)

Seems like there are too many metrics rather that no metric. PAR seems like it could be useful, perhaps not on it's own but still...


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## spooble (Aug 27, 2010)

From what I've read, measuring PAR seems to be best method of determining how much "light" you have. The problem is, there is no easy way of estimating PAR levels. This 50w bulb may be way different than that 50w bulb. And a good reflector can substantially increase the number of micromoles reaching the substrate versus a poor reflector. So really, the only way to know is to get a meter and actually measure the levels in your own tank.


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## Hoppy (Dec 24, 2005)

spooble said:


> From what I've read, measuring PAR seems to be best method of determining how much "light" you have. The problem is, there is no easy way of estimating PAR levels. This 50w bulb may be way different than that 50w bulb. And a good reflector can substantially increase the number of micromoles reaching the substrate versus a poor reflector. So really, the only way to know is to get a meter and actually measure the levels in your own tank.


No question that measuring your own tank with the light you are using is the way to know how much light you have. But, that suggests that we buy a light based on what - the cost, the LFS recommendations, or what? Then borrow a PAR meter and measure. Lets assume you find you have 200 micromols of PAR at the substrate. Now what do you do? You return the light and hope to get your money back? Then buy another light and repeat, etc. until you finally luck into one that gives you the PAR you want?

That doesn't seem like a good plan. If you use this table, at least you have some reason to expect that you will be close to the amount of light you want, and can adjust by raising or lowering the fixture to actually get what you want:









This seems like a much better plan.


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## jarickc (Sep 18, 2010)

I had struggled with trying to figure out lighting for about a week. I was hopping between google, wikipedia, and planted tank forums trying to understand what, Lumen, lux, par, microeinstien, wpg, lumen/in^2 I needed for a high light tank. Finally when I felt all was lost I found Hoppy's post. 
The problem is there is not enough rigor in the discussions going on about light, ferts CO2 etc... This stems from several problems. One we all want different things for our tanks. My personal goal is a stable and natural ecosystem for my plants and fish. Many people seem to feel that for the tank to be healthy the rate of growth must be huge. I understand that fast growth is a sign of health but so to is just healthy slow growing plants. To give an example of this look at Anubias, though we all understand that it likes low light there are people who talk in forums about how fast they can get it to grow with high light. So is the point health or speed? 
So because there is this fixation on speed everything is over done. Normal surface water CO2 concentrations in freshwater are around 10 PPM. So why would some plants die if not in 25+ PPM environments as some have said?
But I have gone off on a tangent, I propose not just a that the measure of appropriate light be something more descriptive such as PAR, which is really microeinstiens/m^2/sec, but that we try to be a bit more systematic in our approach to observations in our tanks. 
Maybe some of use will have the space, time, and money to experiment with different plants in a standardized way and actually produce scientific quality papers that could contribute a lot to the hobby. 
I know that not everyone shares my love of the extremely technical and just do this as a fun hobby. I take pleasure in learning about the world around me and looking at my tanks micro-ecosystem is a way to better understand all the very complex biological, chemical, and even quantum base interactions around me. Hopefully some of you will want to do this and we can make a freely available database with hard science that can guide each other in achieving the tank each of us want.

TL;DR I wish we were more scientific with our tanks.


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## Dave-H (Jul 29, 2010)

Nice chart! Got one that includes LED?


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## Hoppy (Dec 24, 2005)

Dave-H said:


> Nice chart! Got one that includes LED?


Yes, for LEDs there is this:









And, for screw-in CFL bulbs, there are these:


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## plantbrain (Dec 15, 2003)

jarickc said:


> I had struggled with trying to figure out lighting for about a week. I was hopping between google, wikipedia, and planted tank forums trying to understand what, Lumen, lux, par, microeinstien, wpg, lumen/in^2 I needed for a high light tank. Finally when I felt all was lost I found Hoppy's post.
> The problem is there is not enough rigor in the discussions going on about light, ferts CO2 etc... This stems from several problems. One we all want different things for our tanks. My personal goal is a stable and natural ecosystem for my plants and fish. Many people seem to feel that for the tank to be healthy the rate of growth must be huge. I understand that fast growth is a sign of health but so to is just healthy slow growing plants. To give an example of this look at Anubias, though we all understand that it likes low light there are people who talk in forums about how fast they can get it to grow with high light. So is the point health or speed?
> So because there is this fixation on speed everything is over done. Normal surface water CO2 concentrations in freshwater are around 10 PPM. So why would some plants die if not in 25+ PPM environments as some have said?
> But I have gone off on a tangent, I propose not just a that the measure of appropriate light be something more descriptive such as PAR, which is really microeinstiens/m^2/sec, but that we try to be a bit more systematic in our approach to observations in our tanks.
> ...


So, you think there's any $ in doing all this work and research fr a few obscure aquatic plants?

Why not cut to th chase....buy a light meter.
Then see how low you can go...........

There are excellent papers for hobbyist about light and CO2.........folks just do not read them:icon_idea

http://www.tropica.com/advising/technical-articles/biology-of-aquatic-plants/co2-and-light.aspx

Growth still occurs at all light and CO2 levels in this example.........just the RATE changes.


Regards, 
Tom Barr


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## Hoppy (Dec 24, 2005)

It is now possible to rent a good PAR meter, but you do have to send a deposit in order to do so, and if you damage the meter you lose the deposit. If you only need one for a week or less, the rent is a lot less than purchasing one. Try here, for example: http://www.globeaqua.com/rental_par_meter.html

Or, you can buy just the PAR sensor, and use your own millivolt meter to read its signals. That is also a lot cheaper than buying the complete PAR meter, but, of course, you need to have a good millivolt meter too.


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## jarickc (Sep 18, 2010)

I am not saying there is money in it. I am saying it could only lead to a better more well informed community. I said some people may be willing to spend some money cause the science is entertaining. I do think that people are willing to spend money on doing things right. The problem is when they are told about ferts or light they are told "this is what you have to do" instead of "let me explain the kreb cycle and metabolism to you... So now you understand why the CO2 doesn't just need to be off because the plants are not using it but because the plants themselves are off gassing CO2. I may be new to the hobby, but I am not new to science so for my part I will start putting out some good research papers.

Tom thanks for the link. I haven't had a chance to read it through, I will tonight, but just glancing at it I can tell that this is more of the type of thing we need.


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## Dave-H (Jul 29, 2010)

Since so many bulbs are being marketed (in part) to the planted tank enthusiast, it seems like some kind of PAR measurement could become standard.


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## jarickc (Sep 18, 2010)

Dave-H said:


> Since so many bulbs are being marketed (in part) to the planted tank enthusiast, it seems like some kind of PAR measurement could become standard.


Only if as a group we petition them to give it.


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## Hoppy (Dec 24, 2005)

The best we could hope for is something like: Produces 50 micromols of PAR at 20 inches distance (for a light fixture), or produces 50 micromols of PAR at 20 inches, when used with reflectors comparable to XXX. That would be a great improvement in bulb/fixture specifications.


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## jarickc (Sep 18, 2010)

I agree that whatever measurement it was could only be approximate but at leas tit would be something standardized that the consumer could look at and understand what they were getting.

wouldn't it be better to have lights be marketed as XXX par at 20" and fixtures be XXX% light par output at 20 in"? that way you could know what the better fixtures are and what the best bulbs are and get a good idea at the total output based on w/e setup you wind up using?


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## efface (Aug 27, 2010)

pit on your tin foil hats but I feel the industry wouldn't do that because it would create competition which cuts into profits and also poor saps like me end up buying several lights because we buy lights that are too little or too much!


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## Dave-H (Jul 29, 2010)

If you are suggesting that there is a cartel amongst light bulb manufacturers, I'm not so sure  

Even the tacit approval of low-life disposable bulbs seems to be fading away amongst manufacturers, with efficiency and lifespan the new marketing channel of choice. I think that if a bulb manufacturer made a coherent and documented claim that their bulb provided the most PAR per watt/heat/space/etc. they would probably do well.

Maybe there isn't enough interest in the marketplace. I didn't know what a PAR was until I got to this forum


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## Dave-H (Jul 29, 2010)

So, according to that first chart:

I have 1 Coralife dual T5NO bulb strip sitting on a glass top. It's about 19.5 inches from the substrate to the surface of the water, and there is about 1.5 inches of air between the surface of the water and the glass/light.

Per the chart, I think that puts my on the very high end of the low light category. I do have 2 Powerbrite LEDs on the rear of the tank, but the tank is pretty deep so I'm not sure how much that is helping.

I was really hoping to get some medium light going! The plants seem reasonably happy, although the lawn isn't exactly filling in. I'm gonna see how things change when the CO2 system is in place (another week) and take it from there.


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## MrMoneybags (Apr 13, 2010)

@Hoppy

with the chart you posted...is that at substrate level with or without water? and also...what type of reflector are you using?


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## Hoppy (Dec 24, 2005)

MrMoneybags said:


> @Hoppy
> 
> with the chart you posted...is that at substrate level with or without water? and also...what type of reflector are you using?


The chart is based on typical T5HO fixtures, which use very good quality, highly polished aluminum reflectors, generally single bulb reflectors. For AH Supply lights it is using AH Supply reflectors. For T8 lights, it assumes typical white painted flat reflective surfaces behind the bulbs. For PC lights, other than AH Supply, it is based, as I recall, on some fixtures that have very poor quality reflectors, with the bulbs crowded together. The PAR numbers are at the substrate level.

The LED charts are based on no reflector being used, no supplemental optics, just the junction protective optic used by the manufacturer.

It makes no significant difference whether there is water in the tank or air. If there is water, you get some focusing of the light, raising the PAR a bit, and the glass sides of the tank reflect some light back to the substrate, evening out the PAR quite a bit. But, there is no loss of PAR with any water depth we could use in an aquarium. It is easier to get data using no water, so most of what I have measured is in air. But, I have done enough air vs water comparisons to verify that this is a reasonable way to do it.


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## willknowitall (Oct 3, 2010)

what kind of par meters do you guys use
is apogee the go to for most of you
i believe thats a inexpensive one thats good enough


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## mistergreen (Dec 9, 2006)

Where can I find a cheap PAR sensor? I just though of a way to measure the darn thing for about $30.

I believe it's 2 millivolt/umol m^-2 s


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## redfishsc (Aug 29, 2010)

^^^To add to this question, could you suggest a good millivolt meter? I have a standard digital multimeter but it's packed away, and I don't think it reads voltage anything close to that low.


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## mistergreen (Dec 9, 2006)

A millivolt meter is up in the hundreds of dollars.

I have a microprocessor (arduino, $30).... it has an analog input (0 - 1024)... If I change the resolution to 1V, I can get 1mv per unit so I can read the sensor with accuracy.

I looked up the apogee website, their sensor isn't so cheap either... There is a DIY par sensor plan out there but I don't have the mechanical tools to build it... I guess I can make it with found materials but it won't be so accurate. I guess it doesn't need to be super accurate for the average hobbyist.


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## mistergreen (Dec 9, 2006)

Actually, my $60 radioshack volt meter can read millivolts.


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## Jim Miller (Dec 24, 2002)

http://www.tropica.com/advising/technical-articles/biology-of-aquatic-plants/co2-and-light.aspx


Great link!

Jim


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## BostonMike (Oct 20, 2011)

Hoppy said:


> .


Hey Guys,

Ok I am a little confused now:

I just bought a setup I thought was 96Watts for my 28 Gallon Marineland Bowfront. Turns out it is just 48 - but each bulb is a 6500K t5HO

According to this chart, that would be TOO HIGH lighting... is this right even tho the 3 WPG isnt met?


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## OverStocked (May 26, 2007)

BostonMike said:


> Hey Guys,
> 
> Ok I am a little confused now:
> 
> ...


WPG isn't used. Do yourself a favor and stop using it. Just throw it out. Done. Bye bye!

Yes, you are in the HIGH to VERY HIGH catagory of light, for most of your tank. As dave can attest, bowfronts are hard to light front to back. But yours shouldn't be too bad.


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## silvawispa (Oct 11, 2011)

^^^ I misread this!

I couldn't work out why the advice was to throw away the lights....


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## redfishsc (Aug 29, 2010)

mistergreen said:


> Actually, my $60 radioshack volt meter can read millivolts.


I probably have the same multimeter as you (Radioshack) but I'm unsure of it's actually accuracy.


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## BostonMike (Oct 20, 2011)

OverStocked said:


> WPG isn't used. Do yourself a favor and stop using it. Just throw it out. Done. Bye bye!
> 
> Yes, you are in the HIGH to VERY HIGH catagory of light, for most of your tank. As dave can attest, bowfronts are hard to light front to back. But yours shouldn't be too bad.



Would "High light" or "Very High" damage my low light plants, or would it just allow them to grow like crazy!?!


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## Kathyy (Feb 22, 2010)

Low light plants tolerate low light but love lots of light. My Anubias is blooming right now and the Narrow Leaved Java Fern grows fast in bright light. Keep up the fertz and CO2 though.


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## BostonMike (Oct 20, 2011)

Kathyy said:


> Low light plants tolerate low light but love lots of light. My Anubias is blooming right now and the Narrow Leaved Java Fern grows fast in bright light. Keep up the fertz and CO2 though.


Im only using the eco-complete and fish poo as ferts - I am trying to learn more about ferts to avoid nuking my fish plus the gravel i put it while I awaited my ecocomplete raised the [censored][censored][censored][censored] out of my PH 

I am setting up a nice DIY co2 system as well


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