# Is there an LED Watts per gallon equiv?



## AEWHistory (Nov 6, 2008)

Essentially the thread title tells it all. Is there an equivalent measurement for choosing LED lighting like watts per gallon? I suppose one could use how many watts the LED is the equivalent of, but I'm not sure that this really translates for wisely choosing planted tank lighting. I like to maintain 2-3 WPG using plant friendly lights, but I know nothing about moving to LEDs and would like to learn.

Thanks,
Aaron


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## pheo (Nov 28, 2014)

Par.


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## jeffkrol (Jun 5, 2013)

AEWHistory said:


> Essentially the thread title tells it all. Is there an equivalent measurement for choosing LED lighting like watts per gallon? I suppose one could use how many watts the LED is the equivalent of, but I'm not sure that this really translates for wisely choosing planted tank lighting. I like to maintain 2-3 WPG using plant friendly lights, but I know nothing about moving to LEDs and would like to learn.
> 
> Thanks,
> Aaron


Most would say 1)WPG was never very accurate to begin w/ and 2)No there is no "conversion factor"

"Personally" and as a starting point there is some equivalency based on some very good number crunching (primary sources unavailable at the moment but based on some decent measurements).

1/2 to 1/3 watts of LED'S VS T5/8's....

One example is "if" you can do this:


> The bottom line is 'watts per gallon' can be used when comparisons are "apples to apples" such as one Patented High output LED emitter of the same brand to another, but not when comparing a T8, to a T5 to a T2 , to a Metal Halide and especially to an LED.
> An example of an "apples to apples" comparison would be the Patented emitters used by TMC require .8 watt per gallon (or less) under 24 inches of water for high light requiring reef life (.6 watt per gallon or less for planted freshwater aquariums).


http://www.americanaquariumproducts.com/aquarium_lighting.html
You certainly can "guesstimate" sideways in my book.. 

anyways see table 2:
http://www.advancedaquarist.com/2010/2/aafeature2


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## Dmarksvr (Oct 25, 2013)

Coming from the vivarium hobby which was a lil late to the PAR party it seems, we typically shot for around 1-3 wpg (on standard tanks up to 24" tall, with under 1.5w reserved for short tanks). In my experience, others and what I can glean from pics, vids and forum posts it seems like .75-1.75 wpg of led lighting is translating to roughly the same or better brightness to our eyes, and plant growth. On tanks less then 12" or significantly moved 24"tall you have to augment that some. Also if a tank is particularly deep front to back it may need mor light to fill in.

It isn't nearly as precise as PAR and I know it drives some people nuts, but I still feel like watts per gallon can get an inexperienced person in the ball park at least. I like to error on the side of to much light since you can usually raise it, or diffuse it.

They also nned to account for optics and stuff. Like 20 watts of 1w LEDs with lenses is going to have more punch at 18" then 20w worth of a bunch of 120degree .2-.5 watt tiny LEDs probably.

Also in the vivarium hobby we don't have to usually deal with reflection off the water surface or loosing useful wavelengths as they travel through water. That plus many of our popular plants being low/med light means we can often get away with little less then a planted tank might need it seems.

Led is more directional, and I think so far I've found led lighting of the same wattage as older lighting to be about 1.5x (or more) as the old lighting I was using, but I never ponied up for lights with really good reflectors and I have almost no experience with metal halide so take that with a grain of salt. But what I'm getting at is if that entire t-5 or cfl bulb was blasting straight down and not bouncing off a reflector and/or lost some of its brightness after the first few months then it seems like it would be giving around what the Led is. (Not at.all scientific) 

And if you can find a.similar sized tank growing things you wanna grow and doing it well then you can use their wattage as a starting point probably.


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