Can MH be mounted 5 feet away from tank?

[dmc888]

I was wondering if mh can be mounted 5 feet away from the tank.
Are they really that strong.
My lfs has just started a new setup like that.
4-5 ft distance with an open top 20g long tank.
Lights bolted to the ceiling at an angle towards many 20g tanks.
He told me light travels alot farther thru air then water.
Which i believe but 5ft away.
The tanks had corals and anemones in there.
They just installed the lighting.

 

[dmc888]

Probably would get a nice tan from the lighting.

 

[solonfairy]

8-12" is optimal for light spread and intensity
light spread goes down the closer the bulb gets to the tank
intenisty goes up the closer the bulb gets to the tank
around 8" for halides seems to be the best bet

 

[coryherb]

I am obviously not an expert. But...logically, light disperses in all directions, the reflectors attempt to initially reflect the light so that it disperses less. But as the light travels through the air it will disperse as it travels, even what was initially at a perfect 90 degree angle to the water. That will mean you will have more of the light traveling at an angle that is more or less than a 90 degree angle. Having more rays that don't hit at a 90 degree angle means their will be more reflection off the surface.
I am not saying they don't have enough light..but it will definitely be less entering the tank than an equal amount of lighting at a much shorter distance.
IMVHO

 

[acrylic51]

What size or wattage I should say are the bulbs??? It might be fine for a bit, but I have my doubts that the corals and stuff will thrive... Lighting fixture companies do have recommendations as well as bulb manufactures as to where the light is effective as means as distance from water surface, and would have to think 4-5' is really pushing it, but who knows keep us posted!!!!!

 

[shoimen]

That really does not sound like a smart idea. I think the light would dissipate way too much before reaching the tanks.

 

[dmc888]

I will ask tommorow to see how many watts..
I was thinking that too.
I think they have it like that because the have two rows of tanks.
One bottom row of tanks and the top row of tanks which are behind the lower it and raised .
So they would hit both rows of tanks.
I guess its more cost effective.