# how do i calculate wpg with LED lights



## truenoob (Apr 12, 2010)

are the led lights good for planted tanks? and i just want to do a small 29g tank with 2.5-3wpg how will i achieve this with LED lights?


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## jkan0228 (Feb 6, 2011)

The wpg doesn't apply to many types of lighting including LED's


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## samamorgan (Dec 31, 2011)

truenoob said:


> How do i calculate wpg with LED lights?


You don't.

Watts per gallon doesn't apply, and never has.


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## somewhatshocked (Aug 8, 2011)

Rather than tell you WPG doesn't apply (it doesn't), let's do this:

What are you trying to grow in your tank? Will you have pressurized CO2? What about fertilization?

That'll help us more accurately figure out the level of lighting you hope to achieve.


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## zavikan (Jan 5, 2009)

samamorgan said:


> You don't.
> 
> Watts per gallon doesn't apply, and never has.


And aaactually...Your wrong anyways 

there was an older form of fluorescent lighting (t8 i believe it was, but won't bother checking) that the relation of par and wpg for standard tank depths were close enough that the whole 'rule' came into existence. It's simply been applied in all the wrong ways since then.

Schools out.


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## Hoppy (Dec 24, 2005)

If there had been a time when all successful planted tanks were started during a full moon, it could have been said that planted tanks need "full moon starts", and that "rule" would be seen as wisdom from the experts. That didn't happen, but what did happen was that the easily available fluorescent lights that were used successfully on planted tanks with standard proportions, had enough bulbs that their total wattage was about 2 to 3 times the tank volume in gallons. So the wisdom from the experts was that 2-3 watts per gallon was what a planted tank needed. For that to have actually meant anything light would have to be like KNO3, where you mix a quantity with the water to obtain a concentration that is beneficial to the plants. But, just try to mix 50 watts of light (whatever that means) with 25 gallons of water, then measure the concentration of light in a sample of the water. Good luck.


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## zavikan (Jan 5, 2009)

Hoppy said:


> what happened was that the easily available fluorescent lights that were used successfully on planted tanks with standard proportions, had enough bulbs that their total wattage was about 2 to 3 times the tank volume in gallons.


isn't that what I said?

You use to many words Hoppy


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## samamorgan (Dec 31, 2011)

zavikan said:


> And aaactually...Your wrong anyways
> 
> there was an older form of fluorescent lighting (t8 i believe it was, but won't bother checking) that the relation of par and wpg for standard tank depths were close enough that the whole 'rule' came into existence. It's simply been applied in all the wrong ways since then.
> 
> Schools out.


Actually...I'm not. The older T8 WPG rule _barely_ applied to 3 or 4 standard tank sizes. Once you got much smaller, much bigger, or changed heights, the rule went right out the window because of relative intensity. It was a bad idea to try and start, and remains a bad idea. There are way too many variables in lighting to ever try to standardize it in such a simplistic way. The whole idea is almost as laughable as the rex grigg LSI thing.

Another cool bit of knowledge about things that are passed off as common sense: did you know that you don't need to warm up your car anymore? This does nothing in todays vehicles but wear your engine out faster. Or there's that other cool one: premium fuel improves performance. No, it doesnt.


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## Hoppy (Dec 24, 2005)

zavikan said:


> isn't that what I said?
> 
> You use to many words Hoppy


I still have some left over words.:biggrin:

No, I don't think it is what you said. (about 25 words still to be used!)


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## esworp (Mar 20, 2011)

There's a few nice posts about PAR values. A search should get you what you need, instead of these old farts brow beating you for using terminology from a out of date lighting approach. ; ). 

They're asking about your tank setup, because PAR values hinge on water depth/distance.

LEDs are really nice, though, in general. I was fooling around with them 5 years ago, and its /much/ more of a user-friendly world out there for their reference and use these days.


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## jcgd (Feb 18, 2004)

zavikan said:


> And aaactually...Your wrong anyways
> 
> there was an older form of fluorescent lighting (t8 i believe it was, but won't bother checking) that the relation of par and wpg for standard tank depths were close enough that the whole 'rule' came into existence. It's simply been applied in all the wrong ways since then.
> 
> Schools out.





zavikan said:


> isn't that what I said?
> 
> You use to many words Hoppy


Hoppy didn't really say what you said. You were half right, half wrong. Happy points out where you were wrong.



Hoppy said:


> If there had been a time when all successful planted tanks were started during a full moon, it could have been said that planted tanks need "full moon starts", and that "rule" would be seen as wisdom from the experts. That didn't happen, but what did happen was that the easily available fluorescent lights that were used successfully on planted tanks with standard proportions, had enough bulbs that their total wattage was about 2 to 3 times the tank volume in gallons. So the wisdom from the experts was that 2-3 watts per gallon was what a planted tank needed. For that to have actually meant anything light would have to be like KNO3, where you mix a quantity with the water to obtain a concentration that is beneficial to the plants. But, just try to mix 50 watts of light (whatever that means) with 25 gallons of water, then measure the concentration of light in a sample of the water. Good luck.


+1

We always look for patterns in things and lighting has always been determined the same way. Testing. Not a WPG rule.

It doesn't matter what type of lighting you use. The wattage requirements will be based solely from the efficiency and output of the lighting being used. Even with different fixtures you can require more or less of the same type of lighting to product the same result. For example a given tank could require a three bulb Oddysea fixture or a two bulb tek.

The watt per gallon rule was as accurate for a T8/PC setup as a double bulb T5HO fixture guideline we (some people, some times) throw out today. Both got you into a general area where you will usually be able to cope with the results. They aren't at all accurate except for a small variety of common tank sizes, usually in the range of 40-100 gallons. The key in this range is that most tank heights will range from 18-24" and 24" is usually pointed out as to being tall.

You can have your lighting requirement determined a few ways. Test it with a par meter, which is still only a decent guide, but not perfect. Dig into the data that has been collected (which are in the stickies and all over the forum (and in these stickies it's usually broken down what is often needed (so there is really no reason people are so daunted (don't fear pressurized co2)))) and ballpark what you'll need. And you can always ask Hoppy.


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## samamorgan (Dec 31, 2011)

jcgd said:


> And you can always ask Hoppy.


Nuff' said.


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## Schneeball (Dec 28, 2011)

In the world of LED lighting, proper current through the string is key. Then you use a dimming circuit and wonder if your doing it right. :icon_mrgr


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## Hoppy (Dec 24, 2005)

Schneeball said:


> In the world of LED lighting, proper current through the string is key. Then you use a dimming circuit and wonder if your doing it right. :icon_mrgr


Or, you can borrow or buy a PAR meter and determine exactly how much light you have and adjust it accordingly. If you spend $500 to build a good LED light is another $250 for a PAR meter out of the question? (Probably yes )


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## jcgd (Feb 18, 2004)

Jeez. My basic materials ran me $600+. I think my grand total is around $1500. 

Schneebsall, what you did you mean by "then you use a dimmer cct and wonder if you are doing it right"?

I think you are walking a tightrope if you have a led fixture that isn't dimmable. I suppose you could raise the light and lose the optics of the levels are too high, but I couldn't even have my light on in my living room without the optics. The light scatter was too bright and I was seeing spots. Once I added the optics I can look towards the tank without being blinded. My point is that raising the fixture isn't always an option, or practical. My fixture is fully dimmed (analog dimming) and the fixture is 8" off the ceiling. If I have too much light I'm pretty much hooped. Luckly I can use PWM to bring the intensity down to almost nil. 

Sorry for getting so off topic.


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## WingoAgency (Jan 10, 2006)

Quick asnwer 1: Yes LED is good for planted tank. 
Check this thread out for a complete freshwater noob, not to mention planted tank. He kept only SW fowlr most of his life.
http://www.plantedtank.net/forums/new-york/162783-update-wingo-led-ligts-planted-tank.html

Quick answer 2: WPG. You will have too much light unless you do CO2 and a lot of upkeep with your tank at the WPG you mentioned. I use, the most, 1.5W LED / gallon for that size tank assuming all standard common attributes(such as power leds not strawhead leds) used in the aquarium LED DIY builds. Even at 1.5/G, you mayl still want to use CO2. 

As in any lighting no estimate is accurate but you should be able to live with estimates if you can tell us more details. For example, are you talking about a ready made fixture or DIY? With DIY, you can adjust the properties(but a lot of hassle) by changing things to conform to the common DIY builds available in the web such as lens and driving current.... I probably can lead you to some commercial charts of mine that may be close to your setup up. In fact, I may finally have time to mod my own Bio cube 29 after the show on 20th. I can then measure the PAR with a close similarity as your tank.


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## WingoAgency (Jan 10, 2006)

What are the stuff costing the $900 out of the $1500? Making the build looks beautiful?



jcgd said:


> Jeez. My basic materials ran me $600+. I think my grand total is around $1500.
> 
> Schneebsall, what you did you mean by "then you use a dimmer cct and wonder if you are doing it right"?
> 
> ...


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## jonbar1 (Oct 15, 2008)

For a medium light 29g I use 10 3w Cree XP-G driven by a 700mA driver with 80 degree optics that sits about 5 inches above the aquarium. Mix 1 neutral white per 2-3 cool whites to get that "daylight look".


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