# Question about my lighting.



## daniel89 (Nov 28, 2009)

So for my 10 gallon tank i bought two screw in florescence day light bulbs 6500k They are the energy saver ones that use 24w's but they = a regular 100w light bulb. So heres my question. How many watts is the lighting lol 4.8watts per gallon or 20 watts per gallon.

No one seems to be able to answer this question so i hope someone can help me with this.


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## emc7 (Jul 23, 2005)

Most of the current charts assume flourescent, so unless you are using an old book, I'd say 4.8W. Still kind of high, you should be able to grow some nice plants. But if algae goes really nuts you can repace those with 8W or 11W flourescents screw-ins and have less light in the same fixture.


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## Guest (Jan 5, 2010)

I don't like WPG ratings, and this is why (and some of this I have just learned on another forum).

A watt is not a measurement of light, it is a measurement of energy. So a 100watt light bulb uses 100watts of energy, while a 24 watt light bulb uses 24 watts. So you could have 2 lights with the same light output, but different energy usage. A lot of bulbs make a lot of heat, and are thus inefficient. CFL (compact fluorescent light) is the screw in fluorescent they boast to be efficient and equal to a 100watt condescend, and guess what? It is.

The red and blue color spectrum is best for plants, obviously green is the worst... it bounces off because of the green chlorophyll in the plant cells.

A lumen is not even an accurate measurement though. A lumen is the amount of light perceived to be there by the naked human eye. We see green lights very well (this is why green laser pointers are much "brighter" than red for the same energy consumption).

I hope this shed a little light (haha, i love puns ) on the subject.

And yes, emc7 is correct, the 4.8wpg is correct.


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## TheOldSalt (Jan 28, 2005)

The better unit of measurement for our tanks is PAR, which means Photosythetically Active Radiation. This is the measurement of exactly how much truly usable light of the proper spectrum/intensity is hitting your plants.
Why don't we use PAR all the time, then? Simple: PAR meters are very expensive, very expensive, and most folks can't afford to spend that much for something they'll hardly ever use. Therefore we use cheaper ways of measuring the light which almost work just fine.
Anyway, in a 10-gallon tank, which is pretty shallow, those bulbs you got will give you plenty of light for almost anything you'd want.


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## jones57742 (Sep 8, 2007)

lemons said:


> A watt is not a measurement of light, it is a measurement of energy. So a 100watt light bulb uses 100watts of energy ....


le:

Watt is a measurement of power and a 100 Watt light bulb implies 100 joules of energy/second.

TR


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## bmlbytes (Aug 1, 2009)

Look guys, although a watt wont tell you exactly how much light your plants are getting, its a close enough measurement to understand how much light your plants need. Generally when people talk about light, they specify what type of light they are using so people understand how bright it is. For example in this case if dan were going to specify what type of lighting he had, he would say "I have 48 watts of CFL lighting for my 10 gallon tank." However if he had 20 watts of light and was using a T5 bulb, the light would be different and he would suggest that. When you are shopping at the store, or even online most of the time, they don't have lumens or PAR measurements on them, and many hobbiests dont even know how to use those measurements.

My point is, if you buy a GE 6500k CFL bulb at 24 watts, it is going to be VERY close to another company who makes a 6500k CFL bulb at 24 watts. So whats the big deal? We can still acurately measure those numbers by looking them up, even if we dont know what company.


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## Mikaila31 (Nov 29, 2009)

Yes and no. Depends how accurate a company measures its bulbs. I've compared bulbs of the same Kelvin and there was a noticeable color difference between them. 

My order of importance when it comes to bulbs is: color chart, kelvin, then watts. The color chart/spectrum is the closest you can get to factoring in PAR without a PAR meter. PAR measures the amount of red and blue light, sort of. Just because a bulb is 6500K doesn't mean its great for plants. It needs to have a large red and blue spike for plants. Color temp can vary a 6500K bulb may or may not have this. 

There are also sites online that give you the PAR of a wide number of aquarium bulbs;-). 

Sorry for the OP as this has gotten off topic. But yes your tank has 4.8WPG incandesencts do not work with the WPG rule. It was designed specifically for T8 I believe. We use it on all flourescent type bulbs, but as already pointed out not all types of bulbs are the same.


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## Guest (Jan 6, 2010)

> Watt is a measurement of power and a 100 Watt light bulb implies 100 joules of energy/second.


Yes I know, power is energy 
I didn't go into it joules/second or kwh cuz it's its just more complicated


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