lighting on 1.5g tank - The Planted Tank Forum
 
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post #1 of 13 (permalink) Old 10-22-2004, 06:17 AM Thread Starter
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lighting on 1.5g tank

If you have a 7w clip on aquarium light on a 1.5g aquarium, is it like having 5.6wpg on a bigger tank?
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post #2 of 13 (permalink) Old 10-22-2004, 05:10 PM
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7 watt is low light.
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post #3 of 13 (permalink) Old 10-23-2004, 01:33 AM
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Click over to Rex Griggs website: www.rexgrigg.com

He explains how and why the watts per gallon rule breaks down on both smaller and larger aquariums.

Mike

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post #4 of 13 (permalink) Old 10-24-2004, 02:16 AM
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Green,
I agree with looking at Rex's site! But a quick answer is that plants need a certain level of light before they will grow and be healthy. 7 watts of light is not much light at all so, yes you have a high WPG but still have very low lighting. On my 2.5 gallon tanks I have 20 watts of CF lighting and it is still kinda low!

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post #5 of 13 (permalink) Old 10-24-2004, 04:53 AM
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Can someone explain to me what his article is saying about lighting for small tanks in 'dummy' terms? I am totally lost.
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post #6 of 13 (permalink) Old 10-24-2004, 05:10 AM
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To put it simple, I will use a fake plant for an example! We will call this plant The Dan Plant! The Dan Plant requires medium light, but a minimum of 40 watts of light.

If we were to put the Dan Plant into a 55 gallon tank with 165 watts of light (3.0 watts per gallon) the Dan Plant would do fine.

Now if we put the Dan Plant into a 1.5 gallon tank with 7 watts of light, the Dan Plant would die. Sure there are 4.67 Watts Per Gallon, but it is 1/3 of the 20 watts needed for the plant to survive!

Now that is not technical at all! A plant does not really have a set watts it needs but does have a set illumination requirement. And a 7 watt light just does not have the illumination needed for any plants.

Hope that helps

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post #7 of 13 (permalink) Old 10-24-2004, 05:37 AM
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Now that I can understand. Thank you.

Here is another part that confuses me.
Quote:
* Low light is 12-17 LSI
* Medium light is 20-25 LSI
* High light is 28-32 LSI
* Very high light is over 35 LSI
How do I apply this? But still confused how to figure out the above. Something about watts, lux, and square surface inch right?

So say I got a 5.5g tank I want to keep Lilaeopsis brasiliensis, which is medium to high light from my research. How do I figure the LSI for a 13 watt 6700K and 36 watt 6700K bulb? A 5.5g tank has dimensions about 16" long, 8.5" wide, and 10.5" deep. I knew my 2.5g saltwater tank can't take high light corals because of something, but I would love to know the mathematical/scientific reason behind it.
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post #8 of 13 (permalink) Old 10-24-2004, 05:50 AM
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Oh, didn't read the last part, but tell me if I did it right:

Quote:
Well find the surface area of your tank in square inches.
16" * 8.5" = 136"

Quote:
Then take the LSI number you want to reach.
30 LSI

Quote:
Multiply the surface area by the LSI.
136" * 30 LSI = 4080

Quote:
Take the result and divide it by the LUX rating of your chosen light.
4080 / 6700 = 0.6

Doesn't make sence...what did I do wrong?
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post #9 of 13 (permalink) Old 10-24-2004, 06:01 AM
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Well, I think Rex has a typo on his site. I think the way you figure it out is to take your tank size (136) and divide it by the lux rating of your light.

Now the 6700k is not your lux rating. That is your Kelvin rating (also known as color temperature) which has nothing to do with the lux at all. Dont get me wrong, the Kelvin rating is important (you want 5500-12000k for your plants) but not to be figured in on this equation.

To find the lux rating of your light you are going to have to check with the manufacture or buy a gauge for about $150.00.

To make it simple on you, if you can get a 36w light over a 5.5 gallon tank, you should be able to grow a medium-high light plant.

Now comes the hard part. 5.5 gallon tanks are hard to keep the water parameters stable. Dosing fertilizers and keeping Co2 levels up are a challenge!

If you are going to spend the money for the better lights, you might as well jump up to a 10 gallon or more tank!

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post #10 of 13 (permalink) Old 10-24-2004, 05:43 PM
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The thing is I already have a light fixture and it fits the 5.5g tank not a 10g tank. I bought it from Dr.Foster&Smith. It has 2 18 watt 12" PC bulbs. And it seems all the bulbs I look at online don't tell me lux. Is this light considered decent for keeping medium to high light requirement plants?

I know smaller tanks need alot more care then larger ones. I have a 2.5g saltwater tank for months... I just enjoy smaller tanks.
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post #11 of 13 (permalink) Old 10-24-2004, 06:02 PM
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with 36 watts you should be able to grow medium light plants! Give it a shot!

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post #12 of 13 (permalink) Old 10-24-2004, 10:39 PM
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I have a 2.5 bowfront that has a 10w CF on it and the swords in there are growing fine. Healthy green leaves that are growing (slowly - which is what I want). I also 2 small crypts that are growing at a snail's pace, 1 small java fern that has shown signs of growth (slowly), and java moss. I must admit that the swords are right under the bulb. i dose w/ excel when I remember and flourish (when I remember).

If I were you and already have the equipment, I'd give that 1.5 gal a shot w/ the 7wCF lighting but w/ low lights plants only.
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post #13 of 13 (permalink) Old 10-25-2004, 06:51 PM
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I agree with the some of the science behind the article, but not with the practicality of it. I've had tanks with .75 wpg with amazing growth. My 5.5 USG tank has 1.5wpg and plants grow like crazy -- they release oxygen bubbles and everything. So, yeah, the science is there but plants don't give a hoot about science. In my many years of keeping plants and fish, the wpg rules have never been wrong. So, I would say that as long as the 7 watt bulb is in the right Kelvin range over that small tank, low light plants will do well.

Just IMO & my experience...
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