Distance from bulb to water surface

skeety · 08-16-2006, 01:32 PM

okay guys...

I have a 20" tall tank.

I have 2x250 watt HQI Metal Halide bulbs....both 10K.

2x110 VHO's - actinic.

I'm trying to figure out HOW far above the water surface should the fixture be?

More specifically...what should the distance be from the water surface to the BULB!!

I think I've been keeping my lights too high. Right now, I have the bottom of the fixture (the glass) about 8" off the surface. But it's another 5" or 6" from the glass in the fixture to the actual BULB. Which would put my light source over a foot from the surface of the tank.

again...what's the proper distance for a 250 watt HQI bulb from the actual bulb to the surface of the water.

Justin · 08-16-2006, 02:15 PM

That sounds about right skeety. Only recalling in general recolection though, not sure on specifics for a DE. But that's what I keep my SE 175 at well, technically 11" but Id think since it's a DE, if anything it should be slightly higher than your typical SE brand as there suppose to be more intense. I know to utilize the VHO efficiently they need to be close to the water, within 6 inches or so from the waters surface.

And becuase there halides you dont want em too close, heaven forbid they get a splash and explode over your tank

-Justin

Wiskey · 08-16-2006, 02:50 PM

I like to run my MH with the bulb itself about 6-8 inches up. I have a lux meter and I usually adjust within that range with that.

Whiskey

skeety · 08-16-2006, 03:32 PM

okay...two opposite answers! hahaha

don't have to worry about the splashing...as I have a glass cover on the tank (to protect UV mainly..but splashing also).

so one vote for about right as it is (~11") and another vote for 6-8 from the bulb (which would put my fixture darned near right on the frame of the tank.

I really like this fixture...but I DO think they sunk the bulbs too deep into it.

skeety · 08-16-2006, 03:40 PM

okay...deja vu, only delayed.

I guess it was ALMOST one year ago that I already ASKED this question:

http://thereeftank.com/forums/http://www.thereeftank.com/forums/f6/mh-lights-and-distance-to-surface-55606.html

(didn't really get a good answer then. Got lots of info, don't get me wrong, but no real answer as to the distance)

Fly Guy · 08-16-2006, 03:44 PM

I did a poll on this a few months ago..........

FWIW what i gathered out of it is that most of the people who know what they are doing had them 5-8"...mine were 12 at the time.....they are now 5 on my sps system and 8 on my lps system......
Im not a lighting guy...i do what im told.......

My growth in my sps tank doubled or tripled though i must say.......

skeety · 08-16-2006, 04:44 PM

Fly Guy...you're talking bulb to surface? Or fixture to surface?

Fly Guy · 08-16-2006, 04:48 PM

Im talking bulb.....BUT good point.....im not sure that was clarified...it was assumed

skeety · 08-17-2006, 04:52 AM

Skeety bump^

any more input?

Casey · 08-17-2006, 05:15 AM

Bulb to water surface 8"

skeety · 08-17-2006, 06:06 AM

thank you much!

that's gonna put the bottom (glass) of the fixture about 2-3" inches from my water....

But I'll slowly start lowering it.

BGJ223 · 08-17-2006, 09:20 AM

In an effort to not answer your question, but to give you ideas.
Just get a T5 fixture and put it directly on top of the tank.

Did that answer your question?

Sorry not sure what the correct distance should be