figuring out watts/gallon

[FastFly67]

Say I've got a 10 gallon tank lit by a 23 watt CFL bulb. That would make it out to be 2.3 watts/gallon correct? I was trying to explain this to my father but he insisted that it would be 10 watts/gallon because a 23watt cfl = 100watt incandescent. Who's correct?

[Riiz]

You are correct, its "actual" watt/gallon.

[jpappy789]

Yep, if the light is using 23 watts then it's using 23 watts no matter the bulb. You don't need to convert anything.

[Blown 346]

Just for future reference... When looking for lighting it isnt always the best way to go with how many watts per gallon. That will give you a slate to start with, but dont buy just for watts per gallon. You have to look at the light bulbs intensity, and lighting spectrum to properly get that light to penetrate thru the tank.

[sup27606]

I am a newbie in aquariums, but what I have read so far, watt/gallon rule refers to the amount of light emitted by a T12 fluorescent tube. Since CFLs give out more light for the same wattage than a T12 (1.5 times according to one website), you should compensate accordingly. For example, the light emitted by your 23 watt CFL bulb is equivalent to a 34.5 watt T12 bulb. (23 x 1.5 = 34.5). Therefore your watt/gallon would be 3.45, not 2.3. Here is the website that explains the concept, correct me if I am wrong. http://www.americanaquariumproducts.com/Aquarium_Lighting.html

[KarlTh]

It's only the vaguest of guides, and it's standardised for fluorescent. It doesn't work for incandescent at all.

[petluvr]

Use the ACTUAL wattage as stated above. I would think that 10 wpg of ANY lighting would grow nothing but algae:) I don't think that rule really applies though to tanks that small but I may be wrong.

[FastFly67]

Just for future reference... When looking for lighting it isnt always the best way to go with how many watts per gallon. That will give you a slate to start with, but dont buy just for watts per gallon. You have to look at the light bulbs intensity, and lighting spectrum to properly get that light to penetrate thru the tank.
Ok. According to the package of bulb I've purchased, the light output on these 23 watt CFLs is 1600 lumens.
I just want my plants to grow and the hood/bulb I have right now isn't working. I just can't wrap my brain around number and lumens and intensity. For me I guess it's just going to have to be trial and error type deal.

[bluekrissyspike]

i have 30watts cf over my ten g and i have (low-light) plants in there that seem to be growing well enough. the most important thing you need to know is the k rating. i beleive it needs to be 5000+k in order to grow plants successfully. i'm pretty new to plants too though so someone else could probably confirm this for you.

[TwoTankAmin]

In most planted tanks intensity is more important than K. Plants can thrive from arroud 3,000-12,000K. It is only when you get into the more demanding plants that K may become an issue for the plants. It is more an issue of how it looks to you in most tanks.

[bluekrissyspike]

ahh....i c. thanks for clearing that up.

[Riiz]

I am a newbie in aquariums, but what I have read so far, watt/gallon rule refers to the amount of light emitted by a T12 fluorescent tube. Since CFLs give out more light for the same wattage than a T12 (1.5 times according to one website), you should compensate accordingly. For example, the light emitted by your 23 watt CFL bulb is equivalent to a 34.5 watt T12 bulb. (23 x 1.5 = 34.5). Therefore your watt/gallon would be 3.45, not 2.3. Here is the website that explains the concept, correct me if I am wrong. http://www.americanaquariumproducts.com/Aquarium_Lighting.html


This might hold some truth with a straight or linear bulb, but CFLs are spiral and lose a lot of light through restrike, where the light emitted strikes into the bulb and is lost/wasted.

[jpappy789]

Best idea is to not worry about specific wpg at all...the "rule" breaks down in smaller tanks anyways.