Optimal Orientation of MH Bulbs?

[GMGQ]

My tank is 70gallons, about 24x18x48. My MH lights are about 11 inches above the water surface, so I'm thinking of lowering them at least halfway. While I'm at it, I'm wondering if I should change the orientation of the bulbs/reflectors to get better coverage. What do you guys think about the following configurations?

Currently my 250W MH Moguls + spider reflectors are like this:

Left to Right:


What if I changed them so the tips of the bulbs are facing the front, so that the reflectors cover more area laterally?

Front to Back:


Theoretically it looks like I'll get better coverage from the reflectors. But how much light would actually be reflected, compared to the bulbs running 'along' the length of the tank?:

[Joe Reefer]

I am using the same reflectors, they are mounted perpendicular to the front like the bottom drawing. J&L also says they should be mounted in that manner. FWIW these reflectors work very well.

http://www.jlaquatics.com/phpstore/s...t_ID=pfo-prf12

[Delphinus]

Just a thought, but when I put my lamps in the perpendicular orientation, I made it so that the tips faced back instead of front, so that I wouldn't get blinded too too badly when I would go to feed the fish and so on.

As for orientation it generally depends on the reflector and the shape of the tank. For the ones that are recommended to go perpendicular, it is usually because the shape of the light cast is longer in one dimension than the other, and the shapes of most tanks is that they are longer and higher than they are deep ("deep" in this case referring to the front-to-back dimension). Thus, in a cube tank, say, it wouldn't much matter since the depth is the same as the width, so it would be six-of-one/half-dozen-of-the-other. Another consideration is that if you wanted to have actinics, it's usually easier to shoehorn everything in if it's all parallel.

Anyhow for a 48x18 footprint and Spiderlight reflectors, and no concerns about fitting the supplemental actinic (if wanted), then I would go perpendicular. (I notice in your drawing that the fluorescent tubes fit on the side anyhow.)

BTW what software did you use for those drawings? That's way cool!

[TheReefGeek]

No drawings are showing up for me.

Is your tank 24 high, or 18 high?

It it is 18 high, meaning 24" front to back, then each bulb is lighting exactly 24x24" so it wouldn't matter much.

I voted parallel because I don't keep much stuff right up against the glass, more stuff in the middle, so I wanted the bulbs running down the middle of the tank. This may be negated by a reflector, but my PFO reflectors are meant to run parallel so that iw hat I do.

[GMGQ]

Hah! Very funny that you mentioned about the "blinding" factor. Yesterday I was syphoning out cyano, and I couldnt take the blinding light anymore, so I put on my Oakleys! So this is a good point. I did think about it, but I was wondering... Whichever side the socket is, that area will get less light, right? Being the front of the tank is the deepest (no LR, just the sandbed), I though that it would be best not to have the socket on that side? Or is it too negligible?

Originally Posted by Delphinus

Just a thought, but when I put my lamps in the perpendicular orientation, I made it so that the tips faced back instead of front, so that I wouldn't get blinded too too badly when I would go to feed the fish and so on.

Yes, I currently have (2) 48" T5 Actinic+ bulbs on the front and back of the hood. Since my MH and reflectors are like the first picture now, I have to squeeze in the spider reflectors, so that the reflectors dont cover the T5 reflectors. That's another reason why I'm considering the 2nd picture.

The software I use is Maya by Alias Wavefront. It's the software Pixar uses, haha. (I took a 3D animation course before).

Anyhow for a 48x18 footprint and Spiderlight reflectors, and no concerns about fitting the supplemental actinic (if wanted), then I would go perpendicular. (I notice in your drawing that the fluorescent tubes fit on the side anyhow.)

BTW what software did you use for those drawings? That's way cool!

[Delphinus]

Alias Wavefront -- fabulous. I should have guessed. There was a time I was into designing 3d modeling techniques and animation and visualization although when then steady paycheque came with more mundane things I ended up not pursuing that career line (although there are days I still regret that .. oh well).

I was watching Cars on the weekend and in the opening there was "Pixar - Celebrating 20 Years" and suddenly I realized-- Oh my God-- I'm old.

The problem with Pixar is that they make all other animation films look .. well .. bad. They are awesome. And Alias makes awesome tools. There was a time I would have gone to work for them .... oh well, water under the bridge now!!

...

Anyhow, as far as less light making it to the front of the tank, I didn't really notice that myself. Mostly the shadow that's cast by the socket goes out horizontally anyhow, so no concerns about a dark spot in the tank or anything like that. Also you usually don't have anything right up to the front glass anyhow since that's your viewing pane, so I don't think it's a huge concern. Maybe try it both ways and see if you notice a difference but my guess is that you wouldn't really notice.

[Samw]

Assuming you have the PFO Optimal reflectors mentioned by Joe Reefer and will mount them at 6", I vote for perpendicular. If you have the parallel reflectors, then I would change my vote to parallel. If you have another brand, I would follow what the company recommends (probably parallel).

PFO Website from 2003:

http://web.archive.org/web/200304221...ofit+Items.htm


"OPTIMAL REFLECTOR(Reeflector): This reflector is designed to mount perpendicular to the front of the tank. It is made with 95% reflective aluminum and will put about 40% more light into the tank than a standard flat sheet of reflective metal. "


"PARALLEL REFLECTOR : The parallel reflector is designed to mount parallel with the front of the tank using fluorescents. It is made with 95% reflective aluminum and will put about 25% more light into the tank than a standard flat sheet of reflective metal. "

From Sanjay's Testing I Believe:

Light Distribution for Optimal reflector:


Light Distribution for Parallel reflector:


Using the optimal reflector at 6"-9" from the water surface, the area with the brightest light is greater along the X axis. Notice the shape of the oval near the center is wide.

Using the parallel reflector at 6"-9" from the water surface, the area with the brightest light is greater along the Y axis. Notice the shape of the oval near the center is tall.

Thus, at 6"-9" from the water surface, it is better to mount Optimal reflectors perpendicular to the tank and Parallel reflectors parallel to the tank.

At 12" from the water surface, it looks like both should be mounted parallel.

Info taken from:

http://www.advancedaquarist.com/issu...03/feature.htm

.

[TheReefGeek]

Great info, didn't know about their Optimal reflector. Now I wish I had that instead of the parallel one!

[GMGQ]

Yes mine are the Optimal type. Thanks so much for this info! Definitely the way to go then.

Originally Posted by Samw

Assuming you have the PFO Optimal reflectors mentioned by Joe Reefer and will mount them at 6", I vote for perpendicular. If you have the parallel reflectors, then I would change my vote to parallel.

[TheReefGeek]

GMGQ, where abouts did you buy the Optimal reflectors?