# how much light for my 2.5g?



## CarbonHorizon (Jul 28, 2007)

I bought a 27w fluorescent desk lamp. I shine it on my tank. Now I'm just trying to figure out how many hours a day. 

In the tank I have Anacharis, dwarf hairgrass, banana plant, java moss, crypt wendtii, java fern, and wisteria. 

Tomorrow morning I'm going to test and see how warm the tank gets with only morning light, and then if it's not too high it'll get sunlight in the morning too.


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## Red_Rose (Mar 18, 2007)

CarbonHorizon said:


> I bought a 27w fluorescent desk lamp. I shine it on my tank. Now I'm just trying to figure out how many hours a day.
> 
> In the tank I have Anacharis, dwarf hairgrass, banana plant, java moss, crypt wendtii, java fern, and wisteria.
> 
> Tomorrow morning I'm going to test and see how warm the tank gets with only morning light, and then if it's not too high it'll get sunlight in the morning too.


According to Ms. Walstad's book, the tank should get 10-14 hours of lighting a day. My tank gets about an hour of sunlight on some days but other then that, my two 10w fluorescent bulbs take care of the rest. I leave the lights on for 11 hours a day.


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## CarbonHorizon (Jul 28, 2007)

thanks! i'm just worried because that seems like A LOT of watts, but i'll see


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## Red_Rose (Mar 18, 2007)

CarbonHorizon said:


> thanks! i'm just worried because that seems like A LOT of watts, but i'll see


What most people go by is a certain number of watts per gallon. It's normally 1-2 watts per gallon.


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## newbie314 (Mar 2, 2007)

I have a 2.5 gallon (see signature).
I use a 10W bulb from Marineland (5100k).
Seems good enough.
Yours maybe a little too high.


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## Robinthehood (Aug 11, 2007)

Red_Rose said:


> What most people go by is a certain number of watts per gallon. It's normally 1-2 watts per gallon.


I always have a problem with this watts/gallon thing  thats quoted from time to time, simlpy because the tanks dimensions should be a more heavily deciding factor. Particularily the depth, as the light has to have enough power to reach the bottom foliage. Now dont get me wrong I know and appreciate the time people are taking to help others, that's fantastic,... and with only a few gallons of water here, depth should not be an issue. Just beware of the simplified formulas when dealing with larger or more unusual shaped aquariums.
Good luck to all...


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## Red_Rose (Mar 18, 2007)

Robinthehood said:


> I always have a problem with this watts/gallon thing  thats quoted from time to time, simlpy because the tanks dimensions should be a more heavily deciding factor. Particularily the depth, as the light has to have enough power to reach the bottom foliage. Now dont get me wrong I know and appreciate the time people are taking to help others, that's fantastic,... and with only a few gallons of water here, depth should not be an issue. Just beware of the simplified formulas when dealing with larger or more unusual shaped aquariums.
> Good luck to all...


If you have a problem with it then you should take it up with Ms. Walstad. I was merely telling CarbonHorizon what she suggests in her book.


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## Robinthehood (Aug 11, 2007)

:grouphug:


Red_Rose said:


> If you have a problem with it then you should take it up with Ms. Walstad. I was merely telling CarbonHorizon what she suggests in her book.


So sorry Red Rose I didnt want you or anyone to "take it the wrong way":doh: Perhaps I should have stated my point as a concern instead of problem? :loco: :focus: It still must be recognized that a formula with a 100% range is only a very vague guide at best. (i.e. a 100 gal. tank would need between 100 and 200 watts of lighting- quite a big difference to try and narrow down  -- OR imagine any watt/gallon formula when applied the same to a 55 gal. high and a 55 gal. low:faint: ). My point about tank depth(aquascaping and terracing included) as a more major concern is not unique, but the phyisics of the situation remains :hail: reguardless of the source. Taking this up with Ms. Walsted and all her good intentions is mute as she certainly was not the originator of the formula, but passed it on in good faith, I'm sure:thumbsup:, just as we all do with our expierinces. =D> :grouphug: 
Thanks, RJ
... just trying to help with a different perspective ... :hippie:


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## Chuppy (Aug 5, 2007)

Well if that's a lot of watts... then my tank is too bright already! 20gal. with 102 total wattage.. tht has gotta be alot...


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## uglybuckling (Jun 28, 2004)

If you look at Amano's WPG they're always very high over his smaller tanks. I'm not really sure why it works, but for some reason smaller tanks (especially in the less-than-10-g range) tend to be able to tolerate way higher WPG numbers than larger tanks. 

I'm not 100% sure why this is. I suspect it may have to do with light scatter: smaller tanks lose a higher % of their light out the sides than do larger tanks, and hence a smaller % of the incident light actually winds up shining on the tank/plants. However, I'm really not sure. 

Incidentally I'm not a big fan of the WPG number either. 96W over a 40 long (48x12x16") is more than enough light, that same 96W over a 47 tall (20x18x31") is hardly adequate. 

--Bucky


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## Robinthehood (Aug 11, 2007)

uglybuckling said:


> "Incidentally I'm not a big fan of the WPG number either. 96W over a 40 long (48x12x16") is more than enough light, that same 96W over a 47 tall (20x18x31") is hardly adequate."
> 
> --Bucky


Hello again,:hippie: ... yes I believe you've hit that "magic depth of difference" at 18".:horn: The red end of the visible light spectrum is absorbed to a degree and takes a big hit even at this level. More lux is needed to compensate and push those waves down to the lower levels. 
If I remember reading correctly in rayer: Amano's books, in his smaller aquariums he also uses lots of CO2 along with those high light levels... this no doubt must compensate for the plants' tremendous growth rates...:amen: 
:bounce: ...success to all... :bounce: :wave:


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