Is 12" too high for metal halides

[TBone303]

I have a 135 gallon tank which is 36" deep. My plan is to light the tank with 2 / 250 watt and 1 /150 watt metal halides lights 12" for the surface of the water. Is 12" too high up for my lights?

[Jack04]

dont know, i just got some 175's last night (2 actually for 140 bucks total!!!!

but i was thinkin prolly 9-10" off the watter

[Burgman]

Hi,

I would say 12" is good if you do not have any glass between the lights and the water. You could put them closer if you did have a glass panel over your tank water. You want to keep the MH bulbs away from the splash and salt creep.

Dave

[integlikewhoa]

I think 12 is a bit high. The lower the better light. Why put it so high a waist the light. I would keep it just high enough to keep water splashs off it. Also is this a single ended or double? I have mine around 8-9" off but its hanging so i can adjust it if i needed.

[FishhyRen]

Keep in mind, the intensity of the light follows the inverse square law.... The intensity is reduced at the inverse square of the distance...

Personally, I'd go for a little closer... like 6-9inches

[Biscutz]

I have my 175W SE MH's 4.5 inches from the water surface, and I have had this for 2yrs now. I can honestly say that splashing did cause one bulb to crack, but it was while feeding, and I do lift the canapy when I feed now.

[Sullivmw]

First question, What do you plan to keep ? This is the biggest factor, soft, lps, sps, etc.

Second question, Have you picked out the lights yet ? It all is going to depend on the lights you pick, there is a very large par difference in the 250w lights, for instance, if you are going with 10K XM's then you can keep them 12" off the water. If you go with 15K XM's then you just about need them 1" off...

What people do not research enough is the par output of the lights and what you plan to keep. Check out Sanjay's lighting website, you will see there are 250w bulbs that will out-produce 400w, and there are 175W bulbs that will out-produce 250w.

[TBone303]

I would like to keep a mixed tank of corals

[alten78]

it would be ideal to keep your lights as close to the water as possible, but because the heat halides give off, many keep them 6-12 inches off in attempts to avoid heat issue.

[SDguy]

I keep my 250W DE 14K in a PFO hood with icecap ballast only about 5" above my current tank (24" tall). It's a mixed reef. So in general terms, on a 36" tall tank (which, BTW, is going to be a major PITA to work with) I'd say closer than 12". I think even lighting conservatives that would usually say most people use too much light on their tanks would agree that 36" tall tanks are getting into the 400W range. With 250W and 150W, I'd go pretty close to the water. And hopefully they are DE bulbs.

[notoriousB]

wow - this is interesting. my halides are probably 14-16" off the surface of the water. 2x175 14k hamiltons.

Maybe I'll lower them a bit tonight.

[Sullivmw]

<a href=showthread.php?s=&postid=6657243#post6657243 target=_blank>Originally posted</a> by TBone303
I would like to keep a mixed tank of corals

With a mixed tank, 12" is a good starting point. You can always place the corals higher, lower, etc. If going with a 20K bulb, I would say your SPS will be very close to the top. If using a 6500-10K bulb, then not a problem as long as you watch the placement of your corals.

Here is a general idea of the outputs (ppfd) of various 250w bulbs on a PFO HQI taken from Sanjay's website. As you can see a ballast and color temp and reflector will make a huge difference in what your needs will be. Just remeber you can not take this as a direct comparison, since depth will change many of the parameter, but it gives you a good starting point. Also, once people look at the site, they are suprised about the SE vs DE light output (again does not always align with depth)

http://www.reeflightinginfo.arvixe.com/

XM 10K SE- 182
Phoenix 14K DE - 109
Ham 14K SE - 99
XM 20K SE - 79
Coralvue 20K SE - 58

400W (Blueline)
Ham 10K - 122
XM 20K - 99
XM 15K - 75

[Sullivmw]

<a href=showthread.php?s=&postid=6657837#post6657837 target=_blank>Originally posted</a> by notoriousB
wow - this is interesting. my halides are probably 14-16" off the surface of the water. 2x175 14k hamiltons.

Maybe I'll lower them a bit tonight.

Your sig shows you are keeping softies ? If true, then in almost all cases, 14-16" will work for them. Trust me, most softies can be kept under NO style lights.

[TBone303]

notoriousB have you had good coral growth with you light 14" to 16" high

[Alaskan Reefer]

10" here, which I kind of felt was as high as they should be -- and that's with a 22" deep tank...

[notoriousB]

Your sig shows you are keeping softies ? If true, then in almost all cases, 14-16" will work for them. Trust me, most softies can be kept under NO style lights.
wow I need to update my sig, I'll do that now.

I now have quite a few LPS, still some softies, 3 BTAs, & a deresa clam.

notoriousB have you had good coral growth with you light 14" to 16" high
I have had great results w/ the LPS, anemonies, & clam so far. (and the softies are just in heaven.) Things started growing even better after I changed to the hamilton bulbs from some cheapie 10k's.

After work I'm going to do some measuring and consider lowering my lights some, but I've read that the light really doesn't lower in intesity until it has to travel through the water. There's really no "resistance" from the light passing through the air like there is with the water, so I never gave much thought to lowering the lighting further. I'm sure it's more concentrated the lower it is tho...

[Crusty Old Shellback]

Good info but you guys are missing the main point, his tank is 36" deep. That's 3 feet. I'm running 400W DE MH on my 3 foot deep tank right now at about 12" only because it is a temporary set up in my garage. Even with that amount of light, I still wonder if there is enough light reaching the bottom of the tank.

I recently put in a clam on the bottom and so far he seems to be doing fine. But still I wonder about the depth. It dosen't look all that bright on the bottom. I'd say get them closer and maybe step up to a higher wattage light.

Sanja's site has a lot of good info, unfortunatly he hasn't tested but a couple of the 400W DE bulbs on very few ballast.

[Sullivmw]

<a href=showthread.php?s=&postid=6658318#post6658318 target=_blank>Originally posted</a> by blown63chevy


Sanja's site has a lot of good info, unfortunately he hasn't tested but a couple of the 400W DE bulbs on very few ballast.

I agree, I would like to see more testing on the 400's. I have tanks with 400's and some with 250's, and I still say my 400's are much brighter, but Sanjay's website says I'm wrong, go figure.

He is talking about a 36" tank, but he said a mixed tank, to me that means softies on the bottom, lps in the middle, clams\sps on the top. Not my ideal, but with a 36" tank to the bottom, going 12" off the surface, or 6" off the surface really won't make a world of difference. I would concentrate on the bulb combo and reflectors, maybe some Luminarcs.

[Crusty Old Shellback]

Well some of it depends on what your comparing also. XM 10K's are bright in my book. I have 175 SE XM 10K on my small tank and 400W DE Hamilton 14K on my big tank. The 175 looks much brighter because it's more white than blue.

However, I also ahve Coralvue 20K 400W DE's on the same big tank and the 14K hammes look brighter than the 20K's.

As for the depth, 6" may make a bit fo difference. I can check it out when I get home. I do know that a 36" deep tank is a pain to clean at the bottom. ;)

[Sullivmw]

Tbone303 -

Curious, what are your tank dimensions, 36" deep and 135g, you might have a time getting 3 MH on there with reflectors.


Your right 6" can make a difference, but I still figure 30", or 36", he still is going to be keeping softies on the bottom with 250's.

[Crusty Old Shellback]

True. Even with 400's I'm still looking at only keeping softies/LPS on the bottom. I just hope there is enough light down there for my clams.

I do agree though that 36" deep and 135 G seesm odd. Unless it's a custom made tank. My 135 I had was 6'L X 18"W X 24" T if I remember right.

[Sullivmw]

<a href=showthread.php?s=&postid=6658580#post6658580 target=_blank>Originally posted</a> by blown63chevy
Well some of it depends on what your comparing also. XM 10K's are bright in my book. I have 175 SE XM 10K on my small tank and 400W DE Hamilton 14K on my big tank. The 175 looks much brighter because it's more white than blue.


I would like to see the data taken at bottom of tanks, with water. According to the data a XM 10K 250, beats almost all of the 400w's. Even with PFO HQI, the XM 10K is only 10% different from the 250 to the 400. If it is true in real life scenarios, than most of us using the 400's are wasting our time and money, not to mention my 2 chillers.....;)

[Sullivmw]

<a href=showthread.php?s=&postid=6658654#post6658654 target=_blank>Originally posted</a> by blown63chevy

I do agree though that 36" deep and 135 G seesm odd. Unless it's a custom made tank. My 135 I had was 6'L X 18"W X 24" T if I remember right.

I know, I can't even come up with what the dimensions would be, it would have to be custom.

[droppindeuce]

Good thread...just following along.

[Crusty Old Shellback]

<a href=showthread.php?s=&postid=6658658#post6658658 target=_blank>Originally posted</a> by Sullivmw
I would like to see the data taken at bottom of tanks, with water. According to the data a XM 10K 250, beats almost all of the 400w's. Even with PFO HQI, the XM 10K is only 10% different from the 250 to the 400. If it is true in real life scenarios, than most of us using the 400's are wasting our time and money, not to mention my 2 chillers.....;)

Agree 100 %. Then I could cut my electricl bill back some by going with 250's if they will light a 3' deep tank.

[TBone303]

My measurements are 48" x 24" x 36" and I bought an aqua medic Ocean light and my problem is that the light really does not fit my canopy.

[Sullivmw]

Tbone -

With those measurements, I am not really sure I would go with 3 MH's. Spread will not be your problem at 12" above the surface, with 2 MH, and 2 good reflectors such as Luminarcs, you will have plenty of spread. Save the extra cash, and put a couple 2 ft T5's or VHO in between the 2 MH, and you will be set.

But make sure you understand the issues that Blown63Chevy brings up with the depth. You will need to be planning ahead to make sure the right corals are placed at the right depths. While most of the time too low light will simply stunt\slow the corals, it will also affect the colors, so plan ahead on the rockwork and placement.

Also take your time on the purchase of the bulbs and ballast, as you can see with our discussion, the manufacture along with the spectrum will greatly affect your light output. Check out Sanjay's website and match the bulb with ballast.