# How many watts per gallon(LED lights) do I need for a 75 gallon



## miogpsrocks (Sep 3, 2015)

How many watts per gallon(LED lights) do I need for a 75 gallon? 

Is 100 watts LED light 6500K enough for a 75 gallon tank? 

Thanks.


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## chocological (Nov 13, 2012)

What are the dimensions of the tank? What is the PAR ratings and what light are you using? What is the distance to the substrate? Are you injecting CO2?


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## BBradbury (Nov 8, 2010)

Hello mio...

LED lighting looks nice, but hasn't been worth the added expense as far as using it with my planted 55 and 60 gallon tanks. Your 75G has roughly the same length dimensions as my slightly smaller tanks. The best, most cost effective lighting is standard florescent shop lights. Go to the local hardware store and pick up a 4 light fixture and T8, 32 watt, 6500K, 48 inch shop lights. The cost is roughly $50.00 for the whole setup and provides sufficient lighting for the plants that need low to moderate light. The lighting will last well over a year, before you need to replace the bulbs.

B


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## essabee (Oct 7, 2006)

With 100 watt LED you will have a medium lit tank and although you would not need compulsorily carbon enrichment - you shall have the option to go either the excel way or injected CO2 to enhance your range of plants. In other words great options.


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## flight50 (Apr 17, 2012)

Theoretically, you have to ditch the phrase watts per gallon in this hobby. Lighting has really changed nowadays and the watts per gallon is fairly vague and not informative enough. Watts per gallon was a good rule of thumb prior to lighting options expanding now. A 100w led, 100w t5, t8 and a 100w cfl all put out different lighting. Lighting in today's hobby is more accurately measured with PAR. In a nutshell, its the intensity and spectrum that's the focus. LEDs are a bit more expensive but the way I see it, there are 3 unrivaled pros to them. 1) bulb life which can be 20-50,000 hrs-that can be equal to 10 years or more, very little heat output-it doesn't change ambient temperatures nor the water of the tank and less energy consumption-watts consumed nearly 1/4-1/3 of other lighting systems. If you can expense it, go for it. For me, its a no brainer. I have 9 tanks to light eventually. Supplying them with florescent lighting over time will add up. The wattage they will consume will definitely increase my electric bill. Not to mention trying to find good deals on 36" and 60" bulbs. I treat my electrical outlets as if I had a commercial application. That means that I can only run my circuit at 80% capacity to be on a continuous basis. So I only have 1920 watts to run on a 20amp circuit. Every watt I can save, lowers my energy usage. In colder months, I am sure running heaters alone, can trip breakers.


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## jeffkrol (Jun 5, 2013)

miogpsrocks said:


> How many watts per gallon(LED lights) do I need for a 75 gallon?
> 
> Is 100 watts LED light 6500K enough for a 75 gallon tank?
> 
> Thanks.


all the light you could possibly need.. 
EVO Quad 48 LED Reef Bright (TR)

It is split into 2 separate fixtures so you can turn one on at a different time than another.. 

you will most likely never worry that you don't have enough light..

as to Watts vs PAR well yes, PAR is a better definition of light and w/ LED's one needs to be concerned w/ beam angle and tank depth..(well all light really but it usually isn't a "choice")

THAT said as a starting point 1W / gallon is sufficient for moderate light..
Equiv t5/8 would be 2W

shop light/tubes still can't be beat for PAR/$ but it is getting there..and yes LED has advantages..depending.. 

Oh and 6500K is no "magic" K value, just a somewhat entrenched "legend"..

http://www.apsa.co.za/xenforo/threads/lighting-basics-for-people-new-to-the-aquascaping-hobby.11329/

I neither encourage nor discourage using Watts as long as you understand the basic strength and weakness of both..or how/when they apply:



> The old of idea of Watts per gallon does not hold up to scrutiny and I will make no more mention of it. I prefer to think in terms Watts per square meter as a concept for working out how much light to put over an aquarium. The reason for this is because we measure light as a unit of photons per square meter. The wattage of the lamp is strongly correlated with its light output [4].


NOTE:


> The plants will grow perfectly fine under standard fluorescents (or white LEDs) but will suffer from a poor substrate and a shortage of CO2. CO2 is far more critical than lighting. In fact, the tendency to invest heavily in light over CO2 almost always results in a tank overgrown with algae and a disenchanted aquascaper leaving the hobby.


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## shrimpNewbie (May 6, 2011)

Mars aqua 165w fixtures on evilbay. Get 2 for 165 bucks and run them at 30% power 10 inches from the water. You won't regret it and they're very cheap

Sent from my SM-N910T using Tapatalk


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## miogpsrocks (Sep 3, 2015)

jeffkrol said:


> all the light you could possibly need..
> EVO Quad 48 LED Reef Bright (TR)
> 
> It is split into 2 separate fixtures so you can turn one on at a different time than another..
> ...


Do you own this light? 

I was actually very close to buying this but I thought it might be overkill because I was going to have some fish surface swimmers, I don't inject CO2 and I was unsure if this particular light could do the 50% on since the description was talking about select lights will be on in the 3rd mode. 

Usually, its fully power, off, and the 3rd mode is a partial on mode. 

So do you own this light? 

Thanks.


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## Hoppy (Dec 24, 2005)

The only reasons for not using "watts per gallon" to decide on a light fixture are:
It doesn't guarantee that you will have enough light to meet the demands of the plants, and at least some of them will die as a result.
It leaves you very susceptible to bad algae attacks, especially BBA attacks, because it doesn't guarantee that you don't have so much light that you need good CO2 and very good care of the tank to avoid algae attacks if you have so much light the plants will not have enough carbon available to grow at the rate the light causes them to grow.

But, you might luck out and do fine by using "watts per gallon" to pick a light fixture. And if you don't luck out, you might get so disappointed by the experience that you get depressed, give away your aquarium, causing your significant other to get angry with you, your cat to shun you, and your neighbors laugh at you. It's your choice! >


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## jeffkrol (Jun 5, 2013)

miogpsrocks said:


> Do you own this light?
> 
> 
> 
> Thanks.


no, I build my own.......


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