# Light bulb discussion



## xavierj123 (Aug 24, 2008)

With all the difference light bulbs available on the market for an Aquarium, how do you decide on what to use? For example, on my 55 gallon 48X20X12 tank for freshwater fish and live plants.
Thanking ya'll in advance for you helpful input !


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## Fishsticks (Jul 24, 2008)

Seems like it mostly has to do with what kind of plants you are wanting to grow. If you want to have a nice looking tank, then watts per gallon makes a big difference. I started low with around 2 wpg and am now looking to move closer to 3-4 to get better growth out of my plants. Its still a work in progress, but the plants are responding well to the added light.


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## gheitman (Aug 18, 2007)

It also depends on how much time, effort and money you are willing to put into your tank. If you go the high light route at 3 watts/gallon or more you will need to consider the cost of a pressurized CO2 system. As Fishsticks said, the types of plants you want will determine the amount of light you need. I've got a 29 gallon tank with a 65W CF fixture and it gives me all of the growth that I can handle. Most of my other tanks have even less light.


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## xavierj123 (Aug 24, 2008)

What's the CF in the 65 watt fixture mean???


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## davemonkey (Mar 29, 2008)

xavierj123 said:


> What's the CF in the 65 watt fixture mean???


CF = Compact Flourescent (as opposed to a normal flourescent bulb you'd find in the typical shop light)

Another thing: K = Kelvin and refers to color temperature. Anywhere from 5500 to 10000 K is good for plants. You just have to decide what color you like better. Avoid "Actinic" light. That's for reef tanks and doesn't do much for plants. 
Then, you have to look at spectrum. Ideally, you want a spectrum that plants can use (the right wave lengths in red and blue), but from what I understand (and I may be wrong) most lights within the 5500-10000 K will have at least SOME of that.
Then, there's PUR and PAR, and that's WAY over my head.

There is a really good in-depth sticky about that in the "Lighting" forum.

In case you're curious, I have a 48" tank and use 2 "dual daylight" bulbs (mix of 6700 K and 10000 K). The fixture is 130 Watts (65 for each bulb).


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## OhioPlantedtankguy (Aug 7, 2008)

davemonkey said:


> Avoid "Actinic" light. That's for reef tanks and doesn't do much for plants.
> Then, you have to look at spectrum. Ideally, you want a spectrum that plants can use (the right wave lengths in red and blue), but from what I understand (and I may be wrong) most lights within the 5500-10000 K will have at least SOME of that.


This is a bit confusing, you say avoid Actinic light but if you look at the spectrum chart plants use 420nm light the most effectively which btw is what most Actinic bulbs are,Pure Blue Light.










If this chart is right plants should in theory grow the best under Pure Actinic and Red Spectrum Lights, But i have yet to find a place that sells Pure red light spectrum bulbs.

By the chart, the ideal bulbs would be 400 to 420nm and 620 to 675nm in combination. The 420nm bulbs are easy to find, Pure actinic bulbs but has anyone ever seen 620 to 675nm bulbs?

Mind you all this is assuming that the chart is right, which it was giving to me on another forum in a thread i posted so im not sure on the validity of it.


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## davemonkey (Mar 29, 2008)

Hmm, the actinics I had were 460nm (SmartPaq PC). Maybe it's defferent for different bulb brands?


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## OhioPlantedtankguy (Aug 7, 2008)

davemonkey said:


> Hmm, the actinics I had were 460nm (SmartPaq PC). Maybe it's defferent for different bulb brands?


There are two major types of True Actinic bulbs, the first Peaks at 420nm the Second Peaks at 460nm, those numbers are Peak though, the normal light produced is a bit lower on the scale. But you are right you can get 460nm Peak bulbs.

I run T5 so i have literally dozens of bulb choices, but i still have yet to find "Heavy" red bulbs, But i can get Bulbs rated anywhere from 3000k to 20,000k, Actinic blue, 50/50,Actinic white,Weird pink plant "grow bulbs", Fiji Purple(think Pepto Bismal in the tank thats about what they look like),UVA bulbs,UVB Bulbs and many others. The T5 bulbs Available on the market are mind boggling.

The point though is that the ideal bulbs would be 400 to 420nm and 620 to 675nm in combination. If that chart i posted is right.So i cant see how a 420nm Actinic would be bad, especially if used in combination with a heavy red spectrum bulb.


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## davemonkey (Mar 29, 2008)

I have to wait until I get home to see the chart (work computer has too many security filters). I've been going off Newt's 'sticky' about spectrum:

http://www.aquaticplantcentral.com/forumapc/lighting/38014-lighting-spectrum-photosythesis.html

It say's (not a quote, just compiling the peak usage for chlorophyll a,b and carateniods) the ideal range would be 430-453 in the blue, and 642-675 in the red. Based on that, the 420nm and 460nm actinics would be out of ideal range. 
I'm not saying the chart you have is wrong, I've just been going off the above 'sticky'.

Either way, you're right about the red spectrum not being marketed the same way blue is.

-Dave


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## OhioPlantedtankguy (Aug 7, 2008)

davemonkey said:


> I have to wait until I get home to see the chart (work computer has too many security filters). I've been going off Newt's 'sticky' about spectrum:
> 
> http://www.aquaticplantcentral.com/forumapc/lighting/38014-lighting-spectrum-photosythesis.html
> 
> ...


Wow gonna have to spend an hour digesting all that. When you see the chart i posted it will look alot like the thread you listed its just less detailed lol.

The thing with a 460nm Peak, is that most of the light produced isn't 460nm, that is the Peak, IE the highest point,most of the light falls Lower, so actually a 460nm bulb should fall mostly in the 430-453 range that the thread you site suggests. The Chart i have is more basic, according to it, anything between 400 to 500(higher end is where it starts dropping off between 475 and 500) and 600 to 700 on the higher end, 600 being the point where it starts going up again. In reality Plants can use any light even in the green, the chart i listed is more about efficiency than what can be used, the listed spectrum's 400-500 and 600 to 700nm are used the most efficiently or at least those are the highest peaks on the chart.

If i could find a 600 to 700nm bulb i would be happy to run it in combination with a Antinic bulb just to see if it works well lol.


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## Fortuna Wolf (Feb 3, 2007)

You don't need the actinic bulb even. Every photon that gets absorbed is treated similarly. Since red light photons have 2/3rds the energy of the actinic you can theoretically get more PAR out of only red light.


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