# how best to measure lighting needs



## growingwonders (Feb 12, 2010)

I am trying to locate the most cost efficient option for lighting my 48''X24''X24" (120g) aquarium.
I know that watts per gallon is not an accurate measure any longer and I am also aware of what kelving ratings amount to. I tried thinking in terms of how much light it took to grow hard corals in my 46 gallon bf and on that, I had 300 watts of metal halide. I gues what I am asking is for a measurement of light such as lumens that I would need to able to grow high-light plants, such as cobamba and bunch plants horizontally as ground covers. How to I know hat amount of light is getting ot the bottom of the aquarium? With munch blants and taller swords, they may be getting intenses light, while the plants in the foreground, at substraet level are lacking. I am fairly cretain that metal halide is my best option, but would I do best with 2 150 watt pendants, 1 400 watt fixture, or 2 250 watt pendants, and hoe does one come that conclusion with numbers and measurements as an explanation. A link would be of great help and I have read the stickies here on the lighting forum.
Thanks in Advance,
Drew


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## TAB (Feb 7, 2009)

For that tank, I would personally use 2x 150s and then some tubes for supplmental lighting. 



I have yet to see anyone actually produce a study on y ammount of lumes is need to grow XXX plant or how fast plant X will grown with Y lumes. While I have seen plenty of those studys done with corals.


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## JonnyD (Feb 15, 2010)

I would think that this is a very simple answer.
All we need to determine is whether the region where the plant is grown and the shade condition of it's natural habitat.

eg. I'm looking in building a Lilaeopsis Brasiliensis (uSword) carpet. These are normally are found along the shore of S. America stream.

So I would guestimate daylight which ranges from shaded to direct, ~10K-100K lux.

Grab the lux meter and check the light at the base of your tank with and see if you got enough light intensity.


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## growingwonders (Feb 12, 2010)

TAB said:


> For that tank, I would personally use 2x 150s and then some tubes for supplmental lighting.
> 
> I have yet to see anyone actually produce a study on y ammount of lumes is need to grow XXX plant or how fast plant X will grown with Y lumes. While I have seen plenty of those studys done with corals.


I wonder why such a study has done been done on plants? could it be that it owuld equate to watts per gallon and be rather inaccurate measure for the amount of light needed?
I appreciare yout suggestion of 2 metal halide lamps, with supplemental lighting, but I would prefer one type of lighting and if possible one fixture. I have an open topped tank and I am willing to accomodate a few pendant type fixture, but mutliple and different types is just not what I am looking ofr. if the combo fixtures were easier to afford, I'd not be opposed to using them, maybe I can locate a used one? I still need to continue researchin just how much light is approriate.


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## TAB (Feb 7, 2009)

They make pendents with both types in them.


The reason why I recomend going with 2 lighting types, is twofold.

1 you can taylor the color you want alot easier.
2 often you don't need to have the halides on all day( even in reefs) so its nice to have some light in the tank when the haldies are not on.


watt for watt and dollar for dollar, nothing puts out more light then a halide. They are cheaper to buy, cheaper to run, and cheaper when it comes to bulbs. all around they are a much better deal.

I'd check some of the for sale adds on reef web sites. people are always looking to upgrade/down grade, so you can find used stuff for pennys on the dollar


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## endgin33 (Jun 10, 2008)

Plus, the shimmer from halides is just awesome- but you probably already know that


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## growingwonders (Feb 12, 2010)

TAB,
I do like your consideration towards having another lighting option, when the halides are off...that was a detail that escaped my planning. If I understand you correctly, the 2 150watt halides will be more plenty of light for the plants I mentioned, in the size tank I mentioned and the supplemental light would be for viewing, when the lights are off....not really for plant growth. I may just get a smaller watt bulb and place a third fixture in the center of the tank, with a higher kelvin (bluish cast for a dusk effect), that I could operate when the others are off. Please confirm that the 2 150 watt bulbs are adequate for growing cobamba and Hemianthus callitrichoides (dwarf baby tears) horizontaly?


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## TAB (Feb 7, 2009)

I'm running a single 150 and 2 20 waters over my hex tank(26" deep) my HC is a weed. Every week I have to remove patchs that are several square inchs. I've not tryied Cobamba in my tank, but every thing in my tank grows very fast. I have several stems that will grow a inch a day. I'm only running my halide 3 hours a day, the rest of the 10 hour photo period are the 20 watters. I'm sure they are helping with growth, how much I really can't say.


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## growingwonders (Feb 12, 2010)

Thanks so much...your information was a big help.
I still am struggling to understand the relationship between types of light and useable output, but at least I know what lighting I can use with good results now. Best of growing.


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## TAB (Feb 7, 2009)

you can get good results with tubes as well,I just like halides, but I'm a long time reefer. I'm kind of nuts when it comes to lights. I've had a 400 watter over a 10 gallon and my last large system( the displace was 36x36x28) had a 1000 watter over it. The3 400 watters were not enough...


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## growingwonders (Feb 12, 2010)

I like to go over the minimum myself, but you outdo me! I think I am going with 3 150 watt pendants and using a lower watt bulb in the center at a higher kelvin reating for a more twilight feel, after the daylight bulbs are off.


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## armedbiggiet (May 6, 2006)

My experience is teh same as Tab. Currently growing not thing but HC and mini hair grass under 150watt x2 ADA MH lights... yeap they are like weed and also lots of algae on the glass, although it is the good algae but still need to clean teh glass like every 3 to 4 days. The other tank I have the same setup but less crazy cause I just use 2 x 32watt T8 shop light, HC bubbles everyday but grow alot slower and needed to clean the glass less frequnt + less trimming. These 2 tanks are 75g(48inx?x?), you don't want to over kill on lights when you do planted tank. I did had green water problem on the 2 150watt MH and try everything to stop it than end up getting UV to controllling it.


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