T12---T8---T5

[Blue-Ram101]

Haven't been able to find a clear answer on this, I know the smaller bulbs are more efficient... But in regards to the general wpg, rule, does that change when using bulbs other then T12... Example a 48" T12 is 40 watts and a equal length T8 is 32 watts. So in theory to keep the rule of wpg you would need more bulbs. Which to me would defeat the purpose of having more efficient bulbs?

[etheonut]

I just set up a desk lamp to light a 5 gallon aquarium on my wife's desk. By the, it looks awesome, and it is a single LCD bulb that is labeled as "daylight" in spectrum It looks pretty white, so probably 7,000 K or more.

On the box it has a diagram that says a 2.4w LCD = 13w PC = 60w incandescent. Normally I wouldn't quote the sides of boxes that desk lamps come in, but I have seen similar comparisons. The crux of the story is that watts per gallon is not the end of the story and only really works when comparing apples to apples. As the diameter of the bulb gets smaller ie. more efficient, then the wattage inherently goes down. There are other things to compare such as lumens. I am not an expert on lighting, but I hope this helps.

Kevin

[sumpnfishy]

I'm not sure how the wpg works out but I can tell you that not only would a T5 use less electricity than the T12, it will also put out more lumens for the same length of bulb. They are far better at lighting a tank than the larger bulbs. The T5 puts out about 3 times as many lumens per watt used.
Michael

[mewickham]

There is no clear answer. Bulb output is a complicated thing. The T number is the diameter of the bulb in eighths of an inch 5/8, 8/8, and 12/8. Smaller diameter bulbs are more efficient because they are not so close to the reflector that they block their own light from the top half of the bulb. Some large diameter bulbs have reflectorized surfaces on top of the bulb to reflect some of that light back toward the bottom of the bulb, however.

The watts-per-gallon rule is a general rule to put you in the ballpark. But it's only a guideline. Even two bulbs of the same diameter can put out different amounts of light, depending on spectrum and they style of bulb. There are regular output fluorescents, HO (high output) fluorescents, and VHO (very high output) fluorescent bulbs. Each style produces increasing levels of light in a bulb that is the same size (but requires different ballasts). This includes small-diameter T5 bulbs, which are typically regular output or HO. Make sure you buy the right kind for your fixture!

In general, if your bulb is regular output, the watts-per-gallon rule is fine as is (2-5 watts per gallon). HO bulbs, you can probably change to something like 1-4 watts per gallon. With VHOs, 1-3 watts per gallon.

The best way to measure bulb output is lumens or lux, but few manufacturers put those ratings on the package. So we make do with a watts-per-gallon rule.

And yes, a 32-watt bulb puts out less light than a 40-watt bulb. And I would note that the government's idea of a more energy efficient bulb often really means a dimmer bulb.

[rpddink]

there is a multiplyer for the t12 t8 and t5 bulbs vs. what light is produced but the same waattage. and then you need to check if you are n/o or h/o. also the different ballasts will drive lights differently. I put in a lot of research in this area and found a way to wade threw all the crapy info out in the hobby.
I think the bnest way to do it is pick what kind of light you want for the fish/plants - low,med low, med, med high, high and then we can find the right set up for you.

[rpddink]

so basicly a t5 n/o (normal output) at say 18 watts is 1.38 times more light output than than a t12 at 18 watts. reflectors help too a - a t5 with no reflector puts 50% of its light into thetank and the same bulb with a white reflector puts 90% of its light into the tank.

[rpddink]

oh and the tank shape makes a huge diff...

[Blue-Ram101]

That actually helps A lot, thank you for the info!