# MH Lighting for 8(L)x3(W)x2.5(H) tank?



## dan888 (Jan 8, 2006)

I'm planning to use MH for my new planted tank. Initially, i was thinking of using 4 x 150w MH. But will this be sufficient for depth of 2.5 feet?
For light coverage, MH are generally good for 2 x 2. So if i increase the height of the MH pendant and increase the wattage to 250w to cover 3 x 3 area, will this compensate the light intensity by using 3 x 250 wMH light instead of 4 x 150 w?

Hopefully, somebody can answer my question here soon enough as i'm deciding to purchase the light by end of this week.


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## Bob Vivian (Sep 10, 2004)

On your 4x150W scenario, how low to the tank top is your fixture? 

I have 3x150W MH about 5.5" above water level on my 6'Wx2'H tank. It is more than enough light on my high tech tank.

There are advantages to the 4 lamp set up; more even coverage and lower total wattage. The 250's hung higher will cause more of a light leakage/glare problem. And the add'l heat is a concern.

You'll have to look into a comparison of the long range lamp costs. Replacing 3 250's or 4 150's every year and a half is worth considering.
Hope this helps.

Bob


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## dan888 (Jan 8, 2006)

Thanks for your reply. 
I was thinking of hanging the light at least 1.5 feet from the water surface. 
With 4 xs 150w will this be sufficient to grow glosso well into carpet form?
I'll be running CO2 and chiller set at 28C as well.
Actually, i'm thinking that i can compensate the extra height of the pendant from the water surface by using higher wattage, and i do not know whether this will work or not.


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## gnatster (Mar 6, 2004)

At 1.5 ft above the tank unless the reflectors are incredibly focused there will be incredible amounts of spillover into the room. 

The 2x2 footprint of MH is defined more by reflector design then by wattage. I think you will find that you get more even lighting with 4 150's then with 3 250's. Either one will have the punch to reach the 2.5' depth. 

Are you thinking of using mogel base or HQI type bulbs?

Ballast type?

Reflector type?


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## dan888 (Jan 8, 2006)

The MH light i'm planning to use is actually those for 'billboard' type with Mogul base, but i'll be using 6500K and 10000k light bulb. I've seen others that have successfully using those commercially available MH rather than specific for Aquarium application. Over here in Malaysia, MH light for aquarium are overly priced.
As long as the spectrum of the bulb is suitable for photosynthesis and sufficient coverage and wattage, it should fine, rite?


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## Bob Vivian (Sep 10, 2004)

I don't know how efficient your fixture is but, at a foot and a half above the surface, I assure you that you'll be illuminating half your room, too.

I wouldn't hesitate to lower the suspended height 9" or so. You will get all the light penetration you need.

Don't suspend your fixture at an affixed height and experiment a little. Move it as close to the surface as you can. Again, my light is about 5" above the water. I hung it toward the back half of the tank so I have plenty of room to work. If I need to move a large piece of hardscape in or out I can raise the fixture up out of the way.

Bob


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