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Discussion Starter · #1 ·
I would like to know if the watts per gallon rule is necessary or the only rule to go by with lighting. I just had my LFS replace the 3 t8 bulbs in my 80g corner tank hood with a 36" and a 30" LED strips, I had told them I want to be able to grow high light carpeting plant and to install the lighting I need. I trusted them to install adequate lighting because I don't know anything about it, and this is my first big planted tank. When I got home and looked at the LED boxes, one is 30 watts and the other is 24 watts. That's less then 1 watt per gallon and from what I have read I need about 3-5 watts/gallon. Is this true? Even if I just stick with low light plants I feel less that 1 watt/gallon won't be sufficient. I'm lost, and irritated that I paid 300$ for this lighting"upgrade".. Advice please! ( I have about 100 lbs of gravel, (40 lbs Eco - complete and 60lbs Activ-flora) I also have a large piece of driftwood and some rocks. This displaced quite a bit of water, so does watts/gallon apply only the water in my tank or the capacity of the tank?) It seems brighter then it was but the watts are so low, I am very confused. Please help!

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Many will tell you that this rule is obsolete. Really, if you think about it a 20L tank and a 20H tank won't have the same results/w the same WPG
as the light travels farther in the 20H tank. WPG also was made before LED and applies to those light available when itwas thought up.
That would be the T12/T8/ the T5 were not around then but it applies to them also. I'll give you a link to help you to understand it more. http://www.plantedtank.net/forums/showthread.php?t=184368

But we need to know exactly which lights were used to be able to say anything about good or not. Some LED lights have good spectrums and some don't and still others are lower or higher in Watts but the spectrum
is very important to if it works or not.
 

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Discussion Starter · #5 ·
I'm at work at the moment so I can't look at my lights, however I found one of them on amazon for reference if that helps. (On the box I remember it said they come in Blue, a sort of yellow white and a cooler white, I have one each of the two whites)

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Buy a cheap lux meter from Amazon or Ebay, or a few other internet stores. Prop the lights you are going to use across a couple of chairs, and use the lux meter to measure the light at the distance your substrate will be from the light. Divide that lux reading by 78, and you will be reasonably close to the light intensity in PAR units. If that number is about 20-35 you have low light. If it is more than about 60 you have high light. The total wattage is how much electricity you will be paying for to operate the lights.
 

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Discussion Starter · #8 ·
Thanks for the help! It looks like it's the PAR units that are important. I will need to look that up and learn more about it, I'm new to the lighting stuff. Are the numbers (6500K for example) important at all, I don't know what it means.

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I would check into what Hoppy is saying for a more accurate knowledge of what
you have there. How tall is this tank ?
 

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Thanks for the help! It looks like it's the PAR units that are important. I will need to look that up and learn more about it, I'm new to the lighting stuff. Are the numbers (6500K for example) important at all, I don't know what it means.

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k "rating" is the color temp.. see:


10,000K will look "blue white" 3000K will look "yellow white"..
6500k is considered "daylight" color temp..

It only indirectly matters to plants.. but matters to color rendition and visual look.........

Next.. what plants "eat" re light............


Plants love blue and red colored light. not so much the rest but nobody really wants a purple looking tank.. So we compromise a bit..

"white" LED's


after understanding what is good you can move on to how much...
Watts/gal is "useable" when you understand the composition of the light.. A 50W green light is NOT even close to say a 50W 660nm Red light in "efficiency of use" for plants.. or PAR ...
 

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Discussion Starter · #15 ·
Ah, thank you jeffkrol. Is there a certain one that is better? And are the PAR units more important or are they connected? I'm not positive as I don't have access to my lights at the moment, but I think one LED bar in my hood is the 10000k while the other is the 6500k.

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Generally higher are used for deep tanks and lower are used in the more shallow tanks
on the K thing. A high percent of the LED's are now either 6500K or 10,000K but people like "Build My LED" have many more options. The Amazon link was not complete enough so I went to the home site of Wave Point and they now have three in white.
6500K(might be 6700K) 8000K or 10,000K
The one you called slightly yellow was likely the 6700K. That one is generally thought to be the best white spectrum for plants although the hydroponics people are now pushing the 5400K bulbs as better.
The meter Hoppy suggested would be more accurate but I'd say you are looking at about 65-75 PAR. Enough to give you an algae issue if you don't limit the hrs per day on it or use CO2. Are they both on one electric line/cord as in just one thing to plug in ?
I would not use those for more than 7 hrs a day till you find out/w that meter just
what it is.
Unless there is a hidden factor, I think you have more than enough to grow even high light plants but definately the med light ones.
 

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Discussion Starter · #17 ·
Hmm, for some reason I couldn't see all of your post earlier. Is there enough blue and red in the "daylight" white? Or will I need to get specific blue and red lights as well. When I add the 3rd LED strip I can grab the one that's blue and white, but will that be enough?
 

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Discussion Starter · #18 ·
Oh, thank you Raymond S., my Post above is directed at jeffkrol, I should have quoted. Still getting the hang of the forum thing.
As for the plug in, they are on separate cords so I can use them independently. I will try to get my b/f at home to text me a pic of the boxes so I can show them and be a bit more accurate
 

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You might check to see which blue it is as the 460 blue is not common, but is the corect(more of it is used by plants) than the 420.
That third graph(thank you jeffkrol) shows that the white has color in the red and blue parts of the spectrum but more so in the blue. It therefor is suffient for plants. The blue and red lights use all of the energy in one spectrum so provide more per Watt so to speak. They also add more color to your tank. The 10,000K seem just brighter but also seem void of much color. As I stated before they are usually used to make deep tanks more brighter.
I would have second thoughts about adding any more till you find out how much you already have. You can be getting yourself into a situation where you might NEED to
use injected CO2 in there.
 

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Ah, thank you jeffkrol. Is there a certain one that is better? And are the PAR units more important or are they connected? I'm not positive as I don't have access to my lights at the moment, but I think one LED bar in my hood is the 10000k while the other is the 6500k.

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Your over thinking this a bit... Your LFS replaced your lights w/ arguably more PAR efficient lighting..
Actually your best course of action is to see IF you can grow what you want THEN complain if not performing as expected..

Not sure how deep your tank is.. (important in what you are wanting to achieve) nor exactly what type of LEDS or optics (also important)

To be honest.. light sounds a bit low, and price a tad high (how is that for non-committal) but it would be difficult to argue IF it indeed works for what you want..
 
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