PDA

View Full Version : lighting question - wattage


Mr Reefer 1690
05/22/2010, 07:33 AM
This may be a stupid question, but, here goes.
If you have a 48 inch tank lit with 250 watts of T5's, is that similar to using 2 250 watt halides. Of course the watts/gallon is twice with the halides, but each halide is only illuminating a limited area beneath it and not the entire length of tank. The T5's are providing 250 watts of illumination to the whole length of the display.
This isn't a question about which is better. In theory, is the above statement correct

thanks

robertcedgar
05/22/2010, 09:22 AM
No, your assumption is incorrect. With the halides, you have 500 watts, 250 watts for each half (2 feet) of the tank. With the T5, the total wattage is only, however, that 250 is over the entire tank (four feet). Logically therefore, the light is more concentrated and stronger with the halides...in fact, twice as concentrated...as each side of the tank has a full 250 watts of light....

zachfishman
05/22/2010, 01:13 PM
No, your assumption is incorrect. With the halides, you have 500 watts, 250 watts for each half (2 feet) of the tank. With the T5, the total wattage is only, however, that 250 is over the entire tank (four feet). Logically therefore, the light is more concentrated and stronger with the halides...in fact, twice as concentrated...as each side of the tank has a full 250 watts of light....

...if a 250watt halide put out exactly the amount of light that 250watts of T5 does. As I understand it, T5s are much more energy efficient than MH. Therefore the MH wouldn't be putting out quite 2x the amount of light as the T5s in this scenario.

cubsFAN
05/22/2010, 03:03 PM
Watts per gallon is old news and has been for some time. Not a good way to figure out lighting scemes. There are too many factors to involve. Reflectors, ballasts, cooling, etc. will all affect how efficient your lighting setup is. I'm thinking that a 48 in 6x54watt bulb ati pm over a 90 gallon tank tank could keep up with some of the lesser 250watt dual metal halides and exceed others as far as par numbers go. When it gets to the bottom of the tank, the halides generally penetrate deeper than t5's, but this is assuming quality reflectors. So in the end I would say your statement does not provide adequate information to give an answer. I'm sure you could construct a t5 fixture and a metal halide fixture that put out similar numbers but what would be the point.

Amphiprion
05/22/2010, 05:07 PM
I believe (unless it has been shown to be different here recently) that both T5s and metal halides have similar efficiency curves. This is especially true if both types of lamps have good reflectors.