How Do You?

[Truck]

how do you people work out the out put from your light and watts per gallon.

because in other posts ive read that if you have a 15watt t8 and use a reflector you double the light input into the water. would that make it the equivalent of a 30watt.

and also people work out WPG by dividing the volume in gallons by the wattage of the lights so if i have a 15watt t8 and a 15 gallon tank it works out at 15 WPG. but if your using a T5 the out put is brighter so it wouldnt be the same. the t5 is about 150% brighter than the T8 so this doesnt make since.
im confused.COM

 

[kevinthecow]

I have this hub where you can connect 3 lights together for my 5g.. They're small lights but strong. They take one little area, though.

 

[RadaR]

how do you people work out the out put from your light and watts per gallon.


because in other posts ive read that if you have a 15watt t8 and use a reflector you double the light input into the water. would that make it the equivalent of a 30watt.

No. Just means you are getting more like 100% of the light's output directed at the tank instead of losing some of it.

and also people work out WPG by dividing the volume in gallons by the wattage of the lights so if i have a 15watt t8 and a 15 gallon tank it works out at 15 WPG. but if your using a T5 the out put is brighter so it wouldnt be the same. the t5 is about 150% brighter than the T8 so this doesnt make since.
im confused.COM

Er, 15W over a 15gallon would be 1WPG.
t5 are brilliant technology and to get a rough idea, think of t5's as double the intensity as a t8. So 15W of t5 over a 15gallon is equivalent to 2WPG.
The WPG rule was formulated on t12 bulbs though. There is a lot of controversy about this rule, personally I found it quite useful and it works for me.

 

[Truck]

what is a t12 in comparison to a t8 is it weaker.

i have a t8 in a 12 uk gallon and im replacing it with 3, 11watt t5s so using that rule i have the equivalent of 5.2 wpg. so i only need to buy 2 really

 

[RadaR]

t12s weaker than t8s.
I don't know if t5 compacts (the bulbs in acrpod) are the same intensity of regular t5s. Regular t5s might be better. Best thing to do is try 2, and then if it's not enough, add the 3rd.

 

[OldMan47]

The T number is a measurement of the bulb's diameter in 1/8ths of an inch. A T-8 is one inch, a T-12 is 1 1/2 inch a T-5 is 5/8 inch. The T number does not determine the brightness of the bulb. That is determined by how the phosphors are placed in the tube and how much energy is applied to make them glow. What does happen is that a large bulb blocks its own light from reflecting back into the tank. This restrike makes the reflectors less effective and makes a large bulb act like it is a large flat light source. That means that half the light is wasted by going somewhere that is not your tank. A T-8 is slightly more efficient on how it uses electricity so a 4 ft long T-8 produces as much light as a 40 watt T-12 but uses a little less electricity at 32 watts. I treat a 32W T-8 as if it is a 40W for purposes of saying how much light I have over a tank because the light output of both is the same. If I have a really good reflector that is designed to reduce restrike in my T-8 I will look at a light that is only marginal for my plants and say that it is enough. I don't try to put a number on it because I really can't. I just know that it is a bit better than the watt rating would say.
There is another whole factor to consider over a small tank. The real light that you need is light per unit area of the tank. Tank areas do not really decrease in a linear fashion so for low light plants you will find that you need at least 1 1/2 to 2 WPG over a small tank while you can get away with 1 WPG over a 55 gallon. The WPG rules were pretty much worked out by people working with 4 ft long tanks so they are wrong for much smaller and much larger tanks. On a truly large volume tank, the light in watt per gallon need never be as high as would be needed over a 55. The same length tank with a double back to front measurement and a slightly deeper water is a 150. It does not need 3 times the light but about double the light for the same light per unit area. If you put all your plants at the back and had the lights over the back, you could probably use not much more than the light over a 55 to get the same results with the plants.

 

[RadaR]

The T number is a measurement of the bulb's diameter in 1/8ths of an inch. A T-8 is one inch, a T-12 is 1 1/2 inch a T-5 is 5/8 inch. The T number does not determine the brightness of the bulb.

Never said it did. But it just so happens that t8 are better than t12s, and t5s are better than both.

Jamie, you might find this useful.