400 watt on 65 gallon

[yummysalt]

Hi all,
I will be placing one 400 watt MH over a 65 gallon tank, and I need some opinion on how high it should be.
The tank is 36"X18"24". I will be keeping some LPS, and SPS later on.
Suggestions?
Oh and I would rather not switch to a different lighting unless it is really that important.
Thanks.

 

[jackri]

You'll really have to acclimate your corals as you may burn anything you put in there. That's a lot of light for the depth of tank which really isn't needed.

 

[nissan577]

i would switch to a 250w MH.

 

[yummysalt]

I already knew about slowly acclimating the corals, but thanks for the suggestion.
I'm thinking about putting it up 14" and want to know if that should be high enough or does it need to be higher?
Again, like I said, I will not be changing to a different wattage bulb at this time, even though I agree with you.
Other suggestions?

 

[nycbob]

remember u cant use a 250w bulb in a 400w fixture. is this going to be an open top aquarium? i would definitely hang the mh a bit higher, like 20 inches off the water.

 

[bmkj02]

You will probably have to fool around with this. Try 20 inches first and monitor the tempature. You will need to run a fan as well to keep temp down. If temp to high will need to run higher. I have 2 400w on my 125g and I placed it at 13 inches with 2 fans.

 

[fender]

I have mine sitting about 12 inches above the water. Running a 20k XM bulb, magnetic ballast, same dimension tank. Heat can be an issue. I see a 1-2* temp increase from when the lights come on to off - I have a hood that is mostly open. I used to have a fan running with the lights from an old humidifier but it finally died after several years of tank duty.

 

[fender]

oh and the deciding factor for me was the fact that having it any lower left shadows on the side of the tank with my particular reflector.

 

[yummysalt]

Originally Posted by nycbob
http:///forum/post/3210362
remember u cant use a 250w bulb in a 400w fixture. is this going to be an open top aquarium? i would definitely hang the mh a bit higher, like 20 inches off the water.
Yes, it is going to be an open top. I will go ahead and start at the 20 inch mark and see how that goes.

 

[yummysalt]

Originally Posted by bmkj02
http:///forum/post/3211728
You will probably have to fool around with this. Try 20 inches first and monitor the tempature. You will need to run a fan as well to keep temp down. If temp to high will need to run higher. I have 2 400w on my 125g and I placed it at 13 inches with 2 fans.
Sounds good. I also do plan to use a 20,000K bulb to minimize the amount of light.

 

[yummysalt]

Originally Posted by fender
http:///forum/post/3211896
oh and the deciding factor for me was the fact that having it any lower left shadows on the side of the tank with my particular reflector.
Great. Looks like you did exactly what I was planning to do. How much water evaporation do you usually lose per day?

 

[fender]

1/4 to a full gallon a day depending on the dryness of the air. When the fan worked, I could see a gallon and a half in the summer during very dry days.

 

[yummysalt]

Thanks for the info everyone.
Now if for some reason, I was to go ahead and go with a 250 Watt bulb. Do I need a new socket? or will it fit the same socket as the 400W? I know I will need a new Ballast. Oh and this is for a single end bulb.

 

[fender]

AFAIK the 250w and 400w use the same mogul socket.

 

[stanlalee]

I dont think the 400w is a big deal. to put over a 65g you'll have to raise it higher than normal to get full coverage. 3ft 65g are 24" deep so too much intensity is not the concern (XM and Radium 20k seem to be the most popular 400w lamps and they put out less PAR than good 10-14k 250w bulbs). 250wx2 is standard MH protocol for a 65g and being 100w more, closer to the water and cross raying most of the center of the short 3ft area provides more heat, intensity and coverage than a single 400w raised for uniform coverage so I'm not sure I get the concern with "power" of a single 400w even though its not ideal vs 2 lamps. I think the real issue will be front to back light overspill raised appropriately or incomplete side coverage lowered to reduce overspill. I've seen a single 400w work really well on a 3'x3'x2' (same as yours with 18" more front to back).

 

[yummysalt]

Excellent info Stanle. Thanks for the full view picture there. I just hooked up the lights yesterday and it looks pretty good. At the moment, the light is probably 12 to 14 inches from the tank, which is creating some shadows. I haven't got the time to modify it, but will raise it up a bit higher until the shadow is minimize. The lighting time frame is also set to 2 hours at the moment and I'll slowly increase the hours over the course of 2 weeks until a total of 6 hours is reached.
Is that enough time for any corals to adapt? or I can increase it to 6 hours in a shorter time period?