MH light Dispersment

[jlehigh]

I had always planned on running three 250W MH over my new tank. (72LX30WX30D) however reading on marine depot they are suggesting 2 MH's with a spiderlight reflector typically cover 6' of tank...

Does anyone have any thought's or experience with this. I already have 2 PFO 250w MH's with spiderlight reflectors.. I can always try out the 2 alone but wanted to see what y'all thought.

PS: Thank you to all that contributed to the lighting discussion a few weeks back! It has helped me out quite a bit.

Thanks,
John

 

[NaH2O]

John, I always thought it was one MH per 2 feet. Not sure if the difference would be the type of reflector or if the MH is HQI? I'll be along for the ride on this one....

 

[jlehigh]

Thanks Nikki,

Common sense tells me the higher the light is over the tank the broader the dispersment, of course it would also mean the lesser the intencity, so you would want to use a lower K bulb like Ushio 6500's..

 

[big t]

I would think that you would want at least to have the 3 250's. If you only use 2 there will be a lot of area that is lower intensity or even down right shady. If you plan on using some vho or pc's or whatever in addition it would probably work just fine w/ only 2 halides, but there would probably be very defined areas of brightness under the halide lamps.

 

[mojoreef]

1 mh will cover two feet of tank with any normal barn style reflector, spyder included. go with three jlehigh, it will be a far better blend with out the black bands.\\

Mike

 

[jlehigh]

Thanks Mike.. It's what I planned for but wanted to be sure before throwing another 225 bones into the project..

 

[Stircrazy]

you can cover 3 foot of tank with 1 Mogul MH, but you will have dimer areas on the side. ideally you should have 1 for ever 2 foot of length.

at 30" wide you might want to off center your bulbs to wards the back so you can pound the majority of light on the reef and not the sand/bare bottom.

Steve

 

[wanareef]

We have a 72" long and it's lit by 2x 250w Saki's w/4x URI super actinics. There is a center brace and I opted not to put a light there. There is some shading on the ends but not too much of a distraction. Go with three and your corals will love ya for it. :lol:

 

[jlehigh]

Any risk having a 250 MH over my acrylic center brace then? It's 1" thick so I wouldn't think so.... better safe then sorry.

 

[DonW]

I really do not think it would hurt it. If your not comfortable with the heat you could just lay a chunk of 1/4 on it.

Don

 

[big t]

Uhhh actually it could cause a big problem. How far above the brace are you going to have the bulb? It is very important that you have adequate ventilation and circulation in your hood. There is a story out there from a guy who had a 450g acrylic tank. He turned on his lights and had accidentally unplugged his fan or something like that. When he came home I believe he said that his center brace was bowed upward due to the heat. I think that he then began to panic and splashed water on to the brace to cool it off. It then broke due to the rapid cooling. So just make sure that you have good ventilation above it for insurance.

 

[jlehigh]

Wow... that won't help me sleep Well the tank will be sitting in my garage so there really won't be a "canopy" and the lights will be mounted at least 14" above the tank if not more. I will also have a larger fan since noise is not an issue.

 

[mojoreef]

Tom I beleive that was with standard bracing, which is only about 3/8 to 1/2. It sounds like Jlehigh has much thicker euro style. I have two 250 watt hqi's mounted about 6 inches above my center brace (about 1 1/4) and no ill effects. I am not a big fan of allowing fans to be blowing on MH bulbs either. the color of the bulb can be changed by cooling or heating the temperature of the bulb.

Mike

 

[big t]

Well I found the story, It was a 1" thick top

http://www.globaldialog.com/~jrice/oddity_page/break.htm

 

[big t]

That is pretty sad huh? I think that guy just made mistake after mistake. Poor guy. He prolly would have been ok if he drained the tank and beefed up all the cracks w/ some extra material and weldon 40.

 

[szidls]

Hey good thread.
Mike what would you suggest for fan placement in a fully enclosed mh canopy with mogul bulb retro? I'm getting ready to cut openings for 2 icecap 4" fans. Was thinking of fans blowing the long length of the canopy. One in and one out. Trying to stay low to the top of the tank and not blowing directly on bulbs.
Thanks Scott

 

[szidls]

^

 

[jlehigh]

I'm definately not Mike but when I was designing a closed canopy with MH instead of using fans I thought to build sort of a barn shaped top with venting out the sides of the top running the lenght of the canopy... theory here is that heat rises and the reflectors keep the light heading downward...

I know it's hard to visualize my description but you get the idea.. Heat goes up, light goes down so you would just need to allow the heat to escape the canopy through vents and the reflectors would keep the light going down to prevent too much leakage..

just a thought...

 

[ereefic]

We are running 3x175w with PFO Reef-flectors (perpindicular) on our 72x18x20 and it is nice and even light all the way across. Therefor, I would go with 3.

 

[mojoreef]

Wow Tom that was brutal. That's not the same guy I thought it was. When you have a brace or something like that let go you gotta drain it and then do the repair. Trying to repair it with all that pressure coming from different places is never gotta come out good.
I think there is something a little bit more to this story though that is being told. Acrylic gets heated up all the time for bending and shaping, I have seen it so hot it gets to the point where you can just roll it in a ball. Seeing a crack like that leads me to believe he splashed a little water on their right off the bat. But who knows. My halides been sitting over top of my brace for over a year and a half now and I have never seen any problems, and it does get hot.

Scott with an enclosed so that you get a need some type of venting no matter what. jlehigh concept sounds like a viable option. If you're just trying to cool the water you be better off blowing a fan on top of the water in the sump.

jlehigh it's good you're not me, the world could only handle two guys as ugly as us


Mike