Metal Halide Light Placement

I was looking to build a box for my lights and was wondering what is the range of height my lights can be since it will be hanging from the ceiling, i plan on making it adjustable in height so we can access the tank if it so happens to be sitting on the tank itself, We are looking to pretty much have as many corals as we can fit.

Its a 100gallon tank:

60"long 20"tall 18"wide

The lights: 2x MH Oddysea 175W 20k Lights and 2x48" T5HO
and 2x 96W 50/50s

In total this is 650W I know that much be too much so the 50/50s are optional to me so i can really just turn off whatever so my wattage range is: 450W - 550W

Placement from birds eye:

_______________________________T5HO
__________________________50/50
______MH ______MH
__________________________50/50
_______________________________T5HO


I also would like to make sure I utilized as much of the light as i possibly can, as they are now they make two cones of light into the tank(atached picture is what i want, not what i have right now)

So can i just build the box, and adjust the height untill the entire tank is covered in the light, or is there a max height to where the wattage becomes ineffective?


-Dan

 

Most folks place MHs at least 6-8" above the water to help decrease the amount of potentially harmful UV radiation, IR radiation (that is heat), and salt spray on the bulbs and reflectors. The downside as you raise the bulbs higher is that the intensity of light decreases with in proportion to the square of distance. That is light intensity decreases pretty quickly with distance from the source. The good news for you is that the intensity doesn't take as big a hit with distance through air as it does with distance through salt water so your 20" tank won't suffer as much loss through water as some poor fool with a 48" tank.

Another thing you'll want to give some thought to is your choice of MH reflectors. Some reflectors give a fairly wide spread while others are tuned to drive a more concentrated beam of light deep into the tank. Ideally you want to have good light coverage for all the areas of your tank but minimal spread of light outside your tank since that amounts to wasted energy and probably a viewing distraction as well.

 

Cool thx for the info, I ended up at 8.5 inches off the water., It isn't done there is still some mods like acrylic bottom and waiting for another bulb in the mail etc etc, but it looks great!

any critique is welcome

http://www.3reef.com/forums/album.php?albumid=642

 

Karma on the reflector comment.
Advanced Aquarist's Online Magazine - Product Review: Analyzing Reflectors: Lumenbrite III, Lumenmax Elite, Lumenmax, and Lumenarc III

 

thx for the link, that some pretty significant data. Reflectors are deffinantly going to be a mod id like to do soon. The oddysea fixture im usingis extremely restrictive on these lights and does beam them in a narrow path down to the tank, but that would involve me compleltely disasembling the fixture and mounting everything on the wooden box i built.

Another idea i had was to mount all lights at the same height, and coat the entire inside of the box with reflective material ( something like mylar-Mylar - Reflectors & Reflective Material ). This would mix all my lights and beam them down directly in the path of the deminsions of the tank. Definantly a big project that will take up a weekend hehe.


Any thoughts?

 

Sounds like an interesting DIY project. I don't see why it wouldn't work... but I don't really know much about mylar.... as far as how durable it is and stuff like that.
I like the hammertone reflectors for less hot spots.
I have an Odyssea also for now. Maybe next year I'll rebuild the light system.

 

I'm generalizing a bit here but I would say that specifically engineered reflectors do a much better job of directing light down into the tank. This allows you to get much more PAR where you need it without having to go up to a more energy hungry bulb/ballast combination. You could save a few bucks up front by going the mylar route but you would lose out in the long run in terms of greater energy consumption for the same amount of light delivered to your corals.

 

I guess what i meant to say was that i would use the reflectors in addition to the mylar. i would have to dissasemble the oddysea fixture to be able to use the reflectors though. the mylar is just to collect all the light thats being absorbed into the wood from
all the lights in general.