Watts and gallon?

[Mitchel]

I often read the advice for a certain number of watts on a certain number of gallons.
for example that 16W is used in 8 gallons
But which light source does that wattage come from? For example, a 16W LED gives more light than a 16W halogen lamp

cheers, Mitch

 

[Tim Harrison]

I think it was mainly used for T8 and T5 fluorescent bulbs. It's a bit of an antiquated system, and was often criticized, but I reckon it was a good rule of thumb for fluorescent bulbs. Other than that I don't really have a scoobies, especially when it comes to LED lights. They all seem to have different outputs. I just buy lights with dimmers these days so I can adjust the intensity as desired.

 

[PARAGUAY]

Agree,and there are some decent budget LEDS what have dimmers and shouldn't break the bank

 

[oreo57]

I often read the advice for a certain number of watts on a certain number of gallons.
for example that 16W is used in 8 gallons
But which light source does that wattage come from? For example, a 16W LED gives more light than a 16W halogen lamp

cheers, Mitch

I was told at one time it was based on t12's.
It is still useable at least to get a rough estimate for " normal" tank sizes.
Halogens or any incandescents were never considered.
Things like overly deep or shallow tanks never worked even back then.
As mentioned above since dimming comes easy to LEDs no harm in " over- lighting the tank, but of course cost.

That said, over time and other people's measurements any rule of thumb regarding t5/8 has to be reduced by 1/2. Personally I lean more to 3/4 led per 1 watt t5 for instance.

I also found some loose correlation between led, wattage,and par.
If the leds are smaller (1/2 watt or so ) and average quality, and the normal 120 degree lensing, at 18" par = wattage.
One assumption is people measured from the light to substrate.

Water depth & light penetration

I am interested whether there is a general rule for light drop off through a (clear) water column unobstructed by shading plants, floating or otherwise. I have inherited an established tank 47 cm deep (40 x 80 cm long and wide), and it will be initially no-CO2, minimal fish, with a strong...

www.ukaps.org

See post #3

 

[Mitchel]

Thank you all for the answers . But I just don't understand why the Gallon/Watt is still used in the era of LED lighting.
I think it's just better to talk about lumens and/or par per gallon

 

[Disaronno]

Myths are difficult to kill off even if it has been proven false or unreliable.

I guess WPG keep getting spread around is because it's the most familiar and easiest term to understand. Comparing light fixtures based on lumens is not perfect either. Two lights with the same photon output with different spectrum can have different lumen values.

PAR, initially, measures the amount of light from 400nm-700nm at a given distance. Relatively recently it has been expanded to include UV-A and far red. That's just the raw PAR value, it doesn't explain how each plant species is able to effectively use that light. Try explaining that to the normal lay person 😗. For the purposes of in hobby discussions, I'd rather much stick with PAR measurements.

 

[oreo57]

Thank you all for the answers . But I just don't understand why the Gallon/Watt is still used in the era of LED lighting.
I think it's just better to talk about lumens and/or par per gallon

Well even par/gallon has it's weaknesses. What depth, what plants?
ALL have limitations except for a par map of your working tank.
I'm probably one of the few to use it in theory. I do own a Seneye so I can get real mesurements.
Its usefulness is to those with nothing.

Now as to Lumens/gal.. worse than wpg in my mind especially with the introduction of RGB lights.
Put in 660nm red leds in place of normal reds and only a small percent of their photons are counted.
Typical white led in blue below. Warm whites would be worse.

The photopic luminosity is approx what a lux meter would measure. W/ a RGB led light you basically are only measuring green ..
Lux is Lumens/area

Gallons/watts can be a good guesstimate if one understands the limitations.
Much is based on actual par data and actual lights.
Ball park guesses can be made but it is a big ballpark.

Crude idea of the photons a lux meter misses for a 6500k t5.
Not near as many as an led.

Btw way those (orchid growers, hort, ect that actually measured PAR for different lights found , in general 1/2w = 1W t5 to generate the same par level.
Datas out there. Combinatin of a bit higher photons/watt and the fact that most leds have way better control of the output.
Tubes 360 plus reflectors.
Leds generally 120 to 90 degrees, no reflector needed.

 

[oreo57]

How decent is the Fluval LED light that comes with the 200L tank?

Thanks oreo, so that would equate to about 8 lumens per litre, well below the 10-20 level that's often quoted for low level plants. Edit: Having slept on it @oreo57 it begs the questions that lumens in and of themselves are meaningless in relation to plant growth, which isn't really ground...

www.ukaps.org

See post #40 to start. Front and back from there has more of my ramblings..

 

[Mitchel]

Very interesting all those charts and data, but a bit too technical for me personally.
It is clear that PAR or PUR give the most reliable values. But, once you know how much PAR your lighting provides on the bottom of the tank, then what?
How do you know which plants grow best with it, and which plant you can use with that amount of PAR value.
There are few lists in circulation that show per plant species how much PAR they need at a certain depth...

 

[oreo57]

Very interesting all those charts and data, but a bit too technical for me personally.
It is clear that PAR or PUR give the most reliable values. But, once you know how much PAR your lighting provides on the bottom of the tank, then what?
How do you know which plants grow best with it, and which plant you can use with that amount of PAR value.
There are few lists in circulation that show per plant species how much PAR they need at a certain depth...

Plant species can be a part of the "plan"
Balancing light with the available CO2 and nutrients is more crucial I'd say.
Then what ever plants you can grow, you can grow.
Some species are just troublesome for some reason no matter what.
Available water "quality"?
Micro nutrient deficiencies?
Allelopathy?

It is not uncommon for plants to grow fine where the "books" tell you they shouldn't.
Your tank will tell you what it can grow better. Be it algae or plants.

That said, doesn't hurt to "read stuff".

Plants

The 2Hr Aquarist’s definitive guide to freshwater aquarium plants for beginners. This guide includes insight to different plant groups and how to choose the right plants for your planted tank.

www.2hraquarist.com

Light spectrum play an important role in rendering colors well visually, and have a significant impact on plant pigmentation for red plants.
Stronger lighting needs to be paired with the other two variables below, as the elevated growth rates also increases demand for nutrients and CO2.

 

[Simon Cole]

How do you know which plants grow best with it, and which plant you can use with that amount of PAR value.

You can make a guess based upon the biome where the plants are found and information included in botanical publications, and often experts can provide guidance. It is also possible to buy a PAR meter that is suitable for aquatic submersion and make approximations as you work with the plants. I am very tempted to get one for Christmas. If you are working with a specific plant species or genus (like filmy ferns, for example), then there are a few people I might be able to direct you to who will be able to share their experience. LEDs can be quite beneficial where they are dimmable because you can modulate lighting conditions to suit plants. I don't think anybody has started work on a PAR-tolerance list for aquarium plants, but I will keep an eye out in case one is published - although it might not be that useful without a PAR meter to hand.

 

[oreo57]

You can make a guess based upon the biome where the plants are found and information included in botanical publications, and often experts can provide guidance. It is also possible to buy a PAR meter that is suitable for aquatic submersion and make approximations as you work with the plants. I am very tempted to get one for Christmas. If you are working with a specific plant species or genus (like filmy ferns, for example), then there are a few people I might be able to direct you to who will be able to share their experience. LEDs can be quite beneficial where they are dimmable because you can modulate lighting conditions to suit plants. I don't think anybody has started work on a PAR-tolerance list for aquarium plants, but I will keep an eye out in case one is published - although it might not be that useful without a PAR meter to hand.

There are some.

LED Par levels for planted tank

Could someone advise what would constitute low/mid/high par levels for led lights at the substrate? I would also assume that par levels at the substrate is what's important. It does not matter the par level at the top of the water levels where some drift wood branches could be with moss and...

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