# How many Lux do I need??



## northey87 (May 24, 2009)

I have a 120gal tank (60" long, 18" wide, 24" tall) and I currently have a Coralife Quad (4x 65w @ 6700k) fixture almost sitting on the tank right now. I also have a Lux meter on its way and was wondering how much Lux and/or PAR I should roughly have for a low light tank, medium light tank and a high light tank? I keep reading that the watts/gal really doesn't apply anymore, so I figured (also was told by LFS) that the best way to measure light was with a Lux meter, but I have nothing to compare it with to know how much more/less light I need to accomlish what I want (a medium to high light tank). Thanks for the help.


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## Hoppy (Dec 24, 2005)

There is no conversion constant that converts PAR (micromols per square meter per second) to lux. The factor would be different for each type of bulb you used since Lux is weighted to match human eye light sensitivity, but PAR isn't weighted. If you use PAR, the ranges are approximately 25 to 45 micromols for low light, 45 to 80 for medium light, and 80 to 120 for high light. If you can borrow a PAR meter, and limit your measurements to only one type of bulb, 10,000K T5HO, for example, you could calculate a conversion factor between the Lux meter and the PAR meter. It might even be close enough for what you want to do to use that conversion factor for all T5 and PC bulbs.


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## northey87 (May 24, 2009)

Where does one find a PAR meter?


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## bploeg (Sep 20, 2004)

I am no expert in this area, but this article seems to do a nice job of explaining the basics.

http://www.sunmastergrowlamps.com/SunmLightandPlants.html

The term medium to high light isn't very precise :wink: but I would say that it could apply to your setup

There are tons of folks out there with similar set-ups that can tell you what they are using, might be easier than measuring it. FWIW I am 'high light' on
a tank similar to yours, I use 150W MH's (6500k) and 4 T5's and have no problems growing anything. I basically found some other tanks I liked and roughly copied the lighting setup. Of course there endless factors to take into account, quality of bulbs, type of bulb T5 vs. PC, spectrum of bulb, quality of reflector, height over the tank, electronic vs. magnetic ballast , depth of tank etc etc 

Of course having a precise measurement is nicer.


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## Hoppy (Dec 24, 2005)

Some local aquatic plant clubs bought a PAR meter so their members could borrow it, a few months ago, when there were some special deals on them. Look for such a club near you, join it and you could borrow their meter. One such club, if it is still in existence, is PAPAS, Pittsburg Area Planted Aquarium Society. They may not have a PAR meter, but it should be close enough to you.


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## northey87 (May 24, 2009)

Well basically, I just want to have the right amount of light, I just don't know the best way to do it. Will my current light setup be enough? Do I need to get a second Coralife fixture to increase my light output? Or should I just ditch the lighting I have now and get another setup (T5's, MH'S,....)? Thanks for the help so far, this lighting thing is extremely frustrating thing for me to figure out.


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## northey87 (May 24, 2009)

What if I ditched the Coralife and went with this http://www.fosterandsmithaquatics.com/Product/prod_display.cfm?pcatid=16770 

Is this a good brand? If it is what do you think of this; get the 48" x 8" (salt water 216w) and then replace the bulbs with this http://www.fosterandsmithaquatics.com/Product/prod_display.cfm?pcatid=13823

That way I would have full control of the amount of light and can use timers to create a full day cycle. Do you think that that would give me the light I am looking for?


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## Hoppy (Dec 24, 2005)

Is this the light you have? http://www.fishtanksdirect.com/48inch4x65wattaqualightfreshwaterbycoralife.aspx
If so, you are getting about 50 micromols of PAR, which is in the low end of medium light intensity, but only in the middle 4 feet of the 5 foot long tank. The ends of the tank will be quite a bit lower in intensity. For best lighting you need a 5 foot long fixture, or even two 24-30 inch long fixtures, end to end.

If you are using pressurized CO2 you can use high light intensity if you want, or any intensity down to around 25 micromols of PAR. But, if you aren't using pressurized CO2, you should limit the intensity to low light - between 25 and about 50 micromols. Obviously it takes a different light fixture depending on which way you are going.


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## northey87 (May 24, 2009)

Yep, that is the light I have, and I do have a pressurized Co2 system. Would something like this be better? http://www.bigalsonline.com/StoreCa...SD-57011##0##13&queryType=0&hits=12&offset=24
If replace the anctic blues with 6700k bulbs? OR should I spend the money and get one like this? http://www.marinedepot.com/60_Inch_...Sunlight_Supply_Inc-SL2123-FILTFIT5SI-vi.html


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## Hoppy (Dec 24, 2005)

http://www.catalinaaquarium.com/product_info.php?cPath=71_190&products_id=1420 is a good light to use, with it hanging about 10 inches above the tank to reduce the intensity and spread out the light better. I haven't read about anyone being dissatisfied with a Catalina light.


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## northey87 (May 24, 2009)

Well, I call my LFS and they have two retrofit kits that have two 60" 80w T5's per set for $147/piece. I am going down there tomorrow to check them out, see if they are worth it. I planned on building a hood anyway so it will work out good if these kits are as good as they say they are.


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## Hoppy (Dec 24, 2005)

northey87 said:


> Well, I call my LFS and they have two retrofit kits that have two 60" 80w T5's per set for $147/piece. I am going down there tomorrow to check them out, see if they are worth it. I planned on building a hood anyway so it will work out good if these kits are as good as they say they are.


That is a good decision! Just keep the bulbs separated by 9-12", so it evens out the light in the tank. Make sure they have clip on individual bulb reflectors too.


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## northey87 (May 24, 2009)

Thanks. I will keep you posted as I go.


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## northey87 (May 24, 2009)

Well, I went to my LFS and took a look at the retrofit kit and I bought em. They are awesome. Thay are made by Sunlight Supply Inc (http://www.sunlightsupply.com/aqua/...T_KIT&title=Fluorescent Lighting&type=product), and paid $147/kit. For now, they are being put on the sideline till I can design and build my hood. Just one more question, how high off the tank should I put the lighting? Thanks for all the help.


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## northey87 (May 24, 2009)

Okay Hoppy, here's a questions for ya. I have been reading some of your posts in the lighting section, and if I understand you correctly, if I place my T5 bulbs further apart I will lose my intensity and lose my "high light". Would four 60" 80w T5HO bulbs spaced 4.5" apart, and placed about 32" above the substrate give me high light? or should I add another pair of bulbs.


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## Hoppy (Dec 24, 2005)

I would expect to get high light with 4 T5HO lights at 32 inches from the substrate, and the lights evenly spaced across the 18 inch depth of the tank. More light would not be beneficial in my opinion.


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## northey87 (May 24, 2009)

Thanks. Thats what I was hoping you would say. I really don't want to drop another $200+ on another retro fit kit and bulbs.


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## plantbrain (Dec 15, 2003)

4 x 80 W is plenty of light, I have a slightly different shape, but I use 4x 54 W on my 120 Gal, make the hood taller if possible BTW and make it easy front and side access, never top access.

I think about 8-12" is ideal.

Run them 8 hours, maybe 9 hours.

That should do well for you.

Regards, 
Tom Barr


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## northey87 (May 24, 2009)

I plan on building my hood about 1' tall which would put my lights about 10" above the water. And making the whole front of the hood itself a giant door to get plenty of access.


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