Light Numbers: FYI

[fencer]

I finally got a chance to measure the LUX rating under my tanks
Thanks Ken/BWA

Light #1 2x 250w MH / 4x 54w T5ho
Light #2 8x 54w T5ho

These lights are about a year old and on average about 15000K

Both lights sit 4in above the surface of the water. The zone where the most growth is occurring is about 10in below the surface of the water

Result: both showed about 5500 lux
- light at the bottom of the tank was 2500 lux
Ken just got a LED fixture and it was doing about 3800 lux at the bottom of the tank( no where near the wattage of either light canopies)
- I found that the greatest growth in the MH tank was along the long axis of the tank and directly under the light...this makes sense as these are point sources
- definitely the T5 had better light distribution
-stags and deep water sps grew better in the MH tank
- pocci and stylos did better in the T5 tank
-colors came out faster in the T5 tank

I am staying with URI bulbs but change the combination a bit to enhance growth

[Palmer]

Out of curiosity how old were the bulbs? I know you said each fixture is about a year old does that include the bulbs?

[fencer]

The bulbs are 1yr old and will be changed out next month. When new i was only getting about 20% more LUX on average

[Palmer]

I am no lighting expert but just for fun i was looking at lumen maintenance (apparently a measure of a lamps lumen output over time) of MH verses T5. The T5 looked about 95% at 20,000 hours of use-

http://www.lrc.rpi.edu/programs/nlpip/lightingAnswers/lat5/pc9.asp

and

Metal halides lumen maintenance appear to be much lower- http://www.lrc.rpi.edu/programs/nlpip/lightingAnswers/mwmhl/characteristics2.asp

This is probably a nice bonus for T5 and perhaps something to consider when evaluating the Lux performace of T5 and MH on your system when at 1 year of existing use?

Although maybe I am completely wrong as i am no engineer!

[fencer]

I will let you know when I replace the bulbs