40 watts better than 20 watts x2? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 8 Old 06-10-2007, 12:59 AM Thread Starter
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40 watts better than 20 watts x2?

I read somewhere today an explanation about upgrading tank lights, saying that simply adding bulbs is not the best solution.

They stated that you should always get lights with the highest wattage, rather than doubling up on lower watt bulbs.

For example, if you had two 20 watt bulbs, the total wattage is 40 watts, but the intensity is still only 20 watts, while a 40 watt bulb has the same output power, but at greater "lumens" (if this is the correct term).

They further suggest to take this theory to the limit and go out and buy compact florescent bulbs at 30-50 watts or so and just throw a couple of those in rather than building complex setups for adding multiple long tubes. The end result, they say, is many watts at great intensity without spending a lot of money or time to set up. (I don't even know if you can buy compact light bulbs that specify temp)

Sounds right on paper, I guess, but I was wondering if anyone here had heard of this....
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post #2 of 8 Old 06-10-2007, 01:14 AM
2 strip lights are better because u can get one just for plants and one for optimum lighting (the white bulb is for plants and the purply one is for color of fish)
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post #3 of 8 Old 06-10-2007, 09:14 PM
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Well it depends on what you want/like.

As for 2x20 watt vs. 1x40 watt, I have never seen anything that says that they are not at least close to being equal with the chance that the 2x20 is actually more than the actual wattage of the 40 watt for reason of manufacturer specs and such. i.e. a 20 watt bulb may actually be 22 watts just so the manufacturer is certain it is at least 20 watts where the 40 watt might be 42 to make sure it is actually 40 giving you 44 from the dual light setup.

As for lumens, wattage doesn't matter at all. The lumens should be used whenever you can find them on a bulb. the higher the lumens the better it should be for the plants (of course you need a good Kelvin rating of 6500 or higher).

For me, when I build me lighting setup I will be using more mulbs than I need to in order to get my wattage because I want as many different K ratings and Lumens as I can get to cover all the needs of the plants and provide the best light I can to get optinmal growth.

So instead of getting a 220 watt fixture for a 55 I will get 4-6 smaller lights so I can choose which spectrums I wants, Kelvin rating and if I want to I can even throw in actinic lighting even though it doesn't contribute to the total wattage but provides a useful spectrum for plants all the same.

So it all comes down to what you want. If you want a single light for ease of building a fixture or changing of lights get one. If you don't mind mix and match and trying to find a good combination for what you like and works best for your tank, get multiple bulbs and have some fun.
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post #4 of 8 Old 06-10-2007, 10:11 PM
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Is 1 40W bulb better than 2 20W bulbs? Not really. The plants directly under that bulb might get more light, but the rest of the tank will get less light. 2 20W lights spreads out the light more evenly through the whole tank. Now if you wanted even better, then 2 40W would be the next step.

Even though it is the same planet, underwater is a whole different world.
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post #5 of 8 Old 06-11-2007, 12:13 AM
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The right spectrum of lighting is the key...

Heres an Article that helps explain the Proper lighting for Aquarium plants:

Acute sufferer of "GHMT"........(Gotta Have More Tanks)
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post #6 of 8 Old 06-11-2007, 08:00 PM
It's all about lumens and spectral needs of the plants. Wattage, for years, has been grossly used as the main factor in determining the correct light for a planted aquarium. I have been campaigning since I joined the forum that the correct factors in determining the best choice of a lamp is intensity(lumens and Kelvins) and spectrum. Thank you f4a for helping me present this source of information as a good rule of thumb for selecting proper lighting for the planted aquarium.
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post #7 of 8 Old 06-11-2007, 11:59 PM
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Herefishy & F4A...I'll be needing your help in the future when I go to plant my 10g. I know nothing about choosing the right plants...but with your help I should be able to get the right type of lighting to help them grow well.
This has been a good informational/learning thread for me...it got me searching multiple sources on the Internet!

Acute sufferer of "GHMT"........(Gotta Have More Tanks)
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post #8 of 8 Old 06-12-2007, 01:21 PM
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Herefishy is exactly right. I actually use a plant gro bulb as one of my two bulbs in my fixture. The wattage is 40, the lumens are like 1250 but the K is only 3500 according to manufacturer specs. It works well for growing plants so don't be afraid to get a bulb that says it is designed for growing plants regardless of the numbers. I have heard of a lot of them being used and they have never let a plant grower down.
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