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FAQs about Metal Halide & Halogen Lights and Lighting & Heat Issues for Marine Systems

Related FAQs: Chilling, ChillersMetal Halides 1, Metal Halides 2, Metal Halides 3, Metal Halides 4, Metal Halides 5, Metal Halides 6, Metal Halides 7, Metal Halides for Small Systems, Metal Halides for 40-200 gal. Systems, MH for 200 gal. Plus Systems, Metal Halide Lamp Issues, Metal Halide Fixture Issues, MH Repair Issues, Compact Fluorescents, Regular Fluorescents, Lighting Marine Invertebrates, LR LightingTridacnid LightingSmall System Lighting,

Related Articles: Metal Halide Light, & Lighting Articles, Coral System Lighting,

MH over heating Hi, Just wondering how to cool Metal halide lamps down would you need a fan built in or an external fan???? what is the best option???  Thanks  <Please read here: http://www.wetwebmedia.com/marcanopies.htm  and where the linked files (above, in blue) lead you. Bob Fenner> 

MH question 2/11/12
Hi Crew,
<Hello Ragu>
Can MH pendants be mounted on the aquarium top? I mean just placing in on the aquarium braces?
<You could if there is no glass cover on the tank but I would not recommend this, too risky, a good chance the fixture may end up in the tank.>
I have a Arcadia series 3, 3 * 150, I am using it for a 6ft L * 2.5 ft W*3 ft height. The thing is I don't have a canopy and the ceiling is now covered with plaster ceiling thus I am not able to find mount points to hang it. Further more my aquarium comes with a cover. My braces are 12.5 mm thick, I am wondering if it can withstand the weight? The lamps can clear the braces thus the light is not hitting on the braces.
<I suggest you go with a pair of pendant mounts which can be screwed to your cabinet and can be adjusted for height.  Take a look here.
If you're handy, you could even put together something similar in design.>
<You're welcome.  James (Salty Dog)>
// ragu

Metal Halide Distance from Water Level (a too-tight fit) -- 12/27/10
I am thinking of adding a 250W metal halide fixture to my 180 gallon tank that is 30" deep.
<<MH is my fave lighting solution for its flexibility re use of reflector types, bulb color and positioning of the bulb (distance from water's surface)'¦and overall aesthetic value (shimmer). Nothing like a good 'single point-source' lighting option, for me>>
I have limited space above the water level due to an existing canopy.
There is a total of 5-1/2" from hood to water level, leaving only about 3" from the intended metal halide bulb to the water level.
<<Too little space>>
I have existing 4x96W power compact fluorescents. Thoughts?
<<Even were we to assume that an unshielded (Mogul base'¦no ancillary UV shield) bulb would not get broken from incidental splashing of tank water on the hot glass tube, both unshielded and shielded (DE'¦used with ancillary UV shield) bulbs will have their output heavily obscured by dried and 'baked-on' salt/calcareous mineral buildup on the bulb/bulb shield very quickly at this distance. Bulbs in such an enclosure and in such close proximity will also transfer much of their heat energy to the tank -- often problematic in of itself. Such confined space also means you'll need to use a small/shallow parabolic reflector, or worse, a simple flat piece of reflective material -- neither of which will maximize the efficacy of the 250w bulb -- something you may need in such a deep tank, depending on the zooxanthellate animals you keep/wish to keep. But even if light intensity is not an issue here, this hood is just too 'tight' for Metal Halide lighting. One option, if you're willing, is to cut openings in the top of the hood and mount good reflectors 'atop' the hood. Or better yet, dispense with the hood and mount quality MH pendants over the tank. But'¦ If modifying or removing the hood is NOT an option then I would look to VHO or T5 lighting, or stick with the afore mentioned PC lighting, for use within this canopy>>

Yet Another MH Question, heat, incl. louver use f'   -- 7/14/10
I read through the Metal Halide FAQ and am still looking for answers for my personal tank (60 gallon - 48x15x18). I have the Current-USA Sunpod 48" 2x150W fixture and, unfortunately, it sits only 4" above my tank water with the stands that come with the fixture. Given this situation, my tank has been running consistently at about 79 degrees from PC lighting up to 83-84 degrees with MH. I just bought the hanging kit for this fixture and planning on raising it the recommended 8" or so above the water. By what degree do you see this helping with the heat?
<A degree or two F.. I would leave off the MHs during the day... in the warm/er months of the year... have them on during the cooler evening hours only>
I understand that I run the risk with a glass top and high heat as well.
I'll look into getting some egg crates but will the heat melt this?
<Look for the Polystyrene variety, about 240 C... vs. acrylic (160 C)>
I assume running an open top will be fine as well, as long as the fixture is well above the water?
One last question- one of the two fans also stopped working in the fixture and am looking to replace it soon. In the mean time, do you recommend an ordinary desktop fan be placed between the fixture and the tank to cool the
fish tank even more?
<Worth using>
I appreciate your help!
Thank you,
<Welcome. Bob Fenner>

(Integral) Metal Halide Fixture Cooling Fans'¦Necessary? -- 01/17/10
Dear Crew,
<<Hiya Joe>>
Thanks again for providing the extraordinary service of WWM! It is a true blessing!
<<We are pleased to be of assistance>>
I have a quick question regarding metal halide lights. I have purchased a Coralife hang on tank 150 watt HQI light. One of the reasons that I chose this unit was the fact that it has its own built in cooling fan. The manufacturer clearly states in the manual that the cooling fan must be used at all times. Here in the Midwest, it has gotten quite cold this winter (-7 degrees F in KS) and frankly, my reef could benefit from the added heat that the light provides.
<<Best not to rely on this as a heat source'¦at the least, an aquarium heater should be employed for consistency/to provide heat during 'lights out'>>
Is the warning to always run the fan while the light is on due to the heat build up in the tank or does it refer to heat build up in the light that could possibly damage the unit and/or bulb?
<<The latter>>
I know that many units do not have fans at all and would guess that they function well despite the high temperatures they produce.
<<Indeed'¦but this depends also on the design of the fixture and the materials used for construction>>
I would prefer to unplug the fan until the weather warms up.
<<Well Joe, aside from voiding the warranty should the fixture fail due to excessive heat, there's the greater fear of fire here (if I recall, there's a lot of 'plastic' making up the inside and outside of these units). I would not use this fixture without the integral fan>>
Thanks again!
Joe W.
<<Happy to share! EricR>> 

Metal Halide Lighting in Open-Top Canopy'¦Overheating Issue? -- 10/13/09
I am in the process of setting up a 75 gallon reef tank and would appreciate your advice on lighting.
I have a 24" Aqualight Pro HQI light system in my garage from a previous tank. It is 150 watts metal halide and 130 watts of fluorescent actinic. I am considering the purchase of another of the same and using both on the tank.
<<Sounds fine... Metal Halide is my fave lighting solution. It provides more 'band for the buck,' can be easily attenuated by increasing the distance from the lamps to the surface of the water and still provide the necessary 'punch' '¦and in my mind, is more aesthetically pleasing than other lighting methods>>
I plan on building a cabinet/canopy above the tank about 4' tall.
<<Excellent'¦the height gives room to hang/adjust the fixtures, and keeps the warm air mass from being trapped at the water's surface. Do also design-in passive or fan assisted air intake and exhaust ports>>
The cabinet will not have a top; that way air will be able to circulate.
<<Even better'¦though a small fan to circulate air will still be of benefit>>
Also, I keep my house at 71 degrees and do not plan on having a chiller.
<<Likely won't be necessary>>
Will the tank be overheated from the lights being in the open top cabinet?
<<Considering the wattage of the MH bulbs coupled with the design of the canopy, I don't think overheating will be an issue>>
Thanks in advance, Terrence.
<<Happy to assist'¦ EricR>>

Metal Halides and center brace question -- 09/26/09
Hi Bob,
I have searched your site for an answer to my particular question but to no success. So here is the questions; more like questions.
I have a 35 gallon tank that is 36" in length. Not sure as to width and height at the moment, I am away from home. I knew someday I wanted it as a reef tank, not sure to the inhabitants as of yet. Right now it is a FOWLR tank with 25lbs. live rock, a 1.5" coral substrate which I will be switching by 1/3rds every two weeks to aragonite sugar grain size sand, two damsels, and a dogface puffer that is 2 1/2 inches long; I have sometime to set up a larger tank for him in the future. Planning ahead on lighting I purchased a Odyssea 36" 442w fixture with 250w 15,000k mh, 2 96w actinics, and 4 lunar led's. Of course the metal halide is directly in the center and I have a plastic brace in the center of my tank. There in lies the problem.
I can't move the light off to either side because the tank is set up in a corner. I have a month before adding corals, so I have some time to figure out this problem. Here are some fixes I thought of. Any of your own would be
greatly appreciated.
Fix 1: Make the fixture a pendulum raised 12" from the tank. Would this be enough to make sure the light won't melt or crack the plastic brace?
Would corals get enough light?
<I would move the pendant off center... NOT above the center brace. Place the corals that need brighter light under the brighter side>
Fix 2: Same pendulum idea only I add 2 aluminum braces equal distance from the center to strengthen the tank incase the plastic brace does melt.
<Nah... Aluminum rots in the presence of salt water... is toxic>
Fix 3: Cover the brace with a fire retardant material and/or incorporate fans.
Are any of these ideas feasible? Have any better ideas?
<See my comment re #1. Bob Fenner>

Lighting A Frag Tank/Reef Lighting 9/3/09
Greetings WWM,
I'm in the process of setting up a 4' x 2' x 12" frag tank. It will be primarily SPS, I was thinking of buying a friends old Sunlight Supply Maristar metal halide/T5 fixture. My only concern is that it is a magnetic ballast which can be rather heavy and loud.
<Mmm, the Maristar fixtures come with dual electronic ballasts. Your friend's fixture must be an old one. All ballasts operate on the magnetic principle, the electronic ballasts incorporate special circuitry to electronically control power to the lamps which makes them more efficient.>
I've also heard they can interfere with radio frequencies if not properly shielded.
<Nonsense. I can set my battery operated radio on top of my non-electronic MH ballast with no RFI noted.>
Another fixture I'm intrigued by is the Aquatic Life HID/T5 fixture. I understand the "spotlight" reflectors are popular in Asia and Europe.
I'm concerned with the lack of fans or any par tests. Have you any experience with these fixtures ?
<This fixture's internal electronic ballasts work in conjunction with a special aluminum housing to help dissipate heat away from the fixture without the use of fans, and, this fixture is not designed to be enclosed. As far as my experience with them, I have none. Would be better to post this question on one of the reef forums where you will get feedback from actual users of this fixture.
James (Salty Dog)><<Well done James. B>>

Glass Tank Brace Question 04/03/09
Dear Crew,
First, thank you all for the great info you provide. I am sure the reef-keeping hobby would not be what it is today without everything you do.
<Mmm... well, am sure we have a pervasive effect, helping others help themselves, their systems, livestock... but don't know re this stmt.>
Now, to my issue. I recently purchased a 60"L x 18"D x 24"T glass aquarium. The glass is 1/2" thick. Both the top and bottom have plastic rims, which are heavily siliconed in place. There is also a center brace at the top, which is 16"W x 1/2". As you've likely guessed, here lies my problem. The tank will be used for a saltwater reef, lit by 250W MH.
<Mmm, wait... only one fixture? I would not do this... see below>
With the brace in place, I could only place MH fixtures at the ends of the tank. Even if usable light could penetrate the 1/2" glass brace, I still would not put a MH lamp over it, as I'm sure it would crack.
<Mmm, not if placed high enough above>
The solution I have come up with would be to remove the brace and have it cut from a 16" x 18" piece into two 8" x 18" pieces. I would then reinstall them, spaced 10-12 inches apart. I think this would leave adequate room for a center light, while still keeping the bracing as close to the center as possible. I could also add 4" braces on the ends of the tank for a little more support if needed. I would appreciate any opinions on this solution. I did consider Eurobracing, but I would rather not have to remove the top rim and buy all the extra glass if not needed.
<Mmmm, no... the bracing glass strips can be placed/secured lower down, below the plastic rim>
Thank you.
Best Regards,
<Well, what you propose could be done; but I wouldn't do it... IF you elect to remove the present brace, you might well be better off installing a "Euro-brace" See WWM: http://wetwebmedia.com/glstkbraces.htm
and/or the Net re... But, if it were me, mine... I'd instead go with either moving the one 250W fixture to one side (looks better than centered) or better, use two such fixtures, even go with smaller wattage (150s), one over each "open" area... All depends on what you hope to accomplish, but looks and function-wise these are better options IMO than cutting out the existing centered brace. Bob Fenner> 

Metal Halide Lighting Over Center Brace? -- 03/17/09
I am getting metal halide's for my 135 gallon (72" X 18" X 22') aquarium.
<<This is my fave lighting option>>
I currently am keeping LPS and some softies but would like to be able to add some clams at a later date.
I would like to put 3 250w bulbs over the tank,
<<Sounds like a plan>>
but am hesitant to put a bulb over the center brace for fear of either cracking the glass or deteriorating the silicone.
<<Keep the bulb a good 6-inches or more above the brace and ensure some airflow (add a small fan, especially if in an enclosed canopy) and this shouldn't be a problem>>
Is this correct or is it possible to put a bulb over the center brace?
<<Can be done>>
If not possible, would 2 400w bulbs light the whole tank well?
<<I think you will be much happier with three of the smaller lamps spread over this 6-foot long tank>>
I realize that most of my inhabitants do not require overly aggressive lighting; would the 400w bulbs prove harmful to my current coral inhabitants?
<<Any wattage HID bulb will prove harmful if the inhabitants are not properly acclimated to the new lighting (see WWM re'¦here and among the linked pages: http://www.wetwebmedia.com/acclimcoralslight.htm)>>
Thanks for the help.
<<Happy to share'¦ EricR>>

Re: 125 Gallon Project. MHs and acrylic tank heat issues  2/23/09 Hey Scott, <Hello Matt.> I was talking to my acrylic manufacturer about placing halide lighting over acrylic tanks. I've had my 150 tank for 2-3 years now and had 250's for the first couple of years, recently switched to 400's 8 months ago. He claimed that the uv will deteriorate the acrylic over time which is true. <Yes.> That's one issue, the other being that the temperature on top of the tank gets around 120 degrees F which expands and contracts the acrylic on a daily basis further weakening the integrity of the tank top. <It does technically.> Many many hobbyists place halides over acrylic tanks so i am wondering how much should I be concerned about this. <Not really, not if it is all done properly.> Even in the best circumstance with a well ventilated canopy, uv still weakens the tank. Do you have any idea how long tanks last under MH lighting? <Indefinitely really, when the lights are placed properly and the canopy is well ventilated. There are acrylic tanks with halides above that have been in service for decades.> I guess it would be fair to say that the higher the wattage...the more harm done...? <It has more potential to.> He told me a horror story of a tank with 1000 watt lights on it, it cracked and water everywhere... <It can happen with 100 watts!> like i said in my last email, I've got a 125 gal. project with 2 x 400's in a 12 inch tall canopy with 2 4" icecap fans blowing in one hole, out the other. What are your thoughts on this whole concept and with this installation in particular? <Well, all of your concerns are valid, things to think about. The ventilation you have is good, other than that you will want to be sure the lights are not placed directly above the acrylic....in other words they need to be situated over the cutouts in the top.> Greatly appreciated once again, -Matthew <Welcome, do check out this link too, the lighting vs. acrylic is discussed here too, and what to do about it.> http://www.wetwebmedia.com/acrylicaqrepair.htm

Re: Lighting Question, MH... 55 gal., SW, waste heat concern     I'm so very sorry to bother you again, but I have run across more conflicting info in the FAQ's and have another question. <No worries, Matt. This is why we're here.> Since my tank is a standard 55gal, would metal halide lighting be too hot and burn everything up? I have seen that it is recommended not to use MH lighting on a 55gal tank, but have also seem recommendations to use 2 150 watt MH pendants above this same setup. All of this conflicting info is starting to get confusing to me. Any input would be greatly appreciated. If the 2 pendants would be fine, how far above the tank should I keep them to minimize evaporation and bleaching of my corals? <First, let me preface this by reminding you that every set up is different. So, just because someone had heat issues with MH lighting over a 55gal that does not mean your set up will as well. Whether your tank will overheat depends on several factors. First, what is the highest temperature your tank has reached with your current lighting method? If it is in the upper levels of the acceptable range, then you should consider using more efficient equipment (such as cooler running return pumps or circulation powerheads) and/or increase cooling (by adding a chiller or fans) before upgrading to MH. Second, not all MH setups are the same as some are terribly inefficient. Consider going with a proper MH set up with a quality electronic ballast like the Icecap 150W ballast and bulb like the Phoenix 14k to maximize efficiency. Review this site for more information on efficiency: http://www.manhattanreefs.com/lighting. For reference, I live in Southern California where ambient temperatures can be quite high in the summer and I am able to hang a 150W MH set up 12" over my 24 gallon Nano Cube. I use a fan to blow cool air over the water surface to increase evaporative cooling and water temperature is table at 80-81 degrees even on the hottest days.> Thanks again Matt <You're welcome. Cheers, Minh Huynh.>

Using Heater Controller For Controlling Halides 9/21/08 Hi Crew, <Hello there Tom, I must apologize for the extremely tardy follow up here. This email was, well, misplaced/lost in traffic.> Just a follow up on this old question. After measuring the actual wattage of my halide ballast/lights, I ended up trying the Aqua Medic Biotherm 1000W heater controller as a halide safety shut-off, and it has been working very well. The wattmeter, a Seasonic Power Angel, measured the halide startup wattage much lower, at about 40 watts, than the peak 515 watt draw after the bulbs were completely lit. The controller seems to treat the halide lights like any other heating element. <It should, I have seen this myself in service for years. I do remember reading your original query back when, if memory serves the controller is rated to 1000 watts? Should be plenty for appropriate lighting on a 130.> I'm using a PFO magnetic ballast. Recently our chiller pump intake got clogged and the tank temperature went up a couple of degrees - as soon as it hit 83F, the lights were automatically shut off until the water dropped below 82F. <Whew, shows it is worth doing even with a chiller. We all invest way more money than planned into our systems, safeguards are always welcome.> Thanks, Tom <Very welcome Tom. It is always rewarding when things 'outside the box' work so well. Have fun, Scott V.>

Lighting Overkill? 1/23/08 I currently have a 65 gallon, 36x18x24, I already have 2 150W halides with 20K radium bulbs. I would like to upgrade to a system that has 2 250W 10K halides with 4 T5 actinics. This would give me around 656W, but that is over 10 watts a gallon. I plan on housing more sps and clams in the future. Should I stick with this idea or go with a less wattage of halide, like 2 175W mogul with T5's. <I would be inclined to stay with your current fixture with bulbs in a better (10K) spectrum.> I currently have DE bulbs and the lighting in question has DE bulbs. I currently have just polyps, some micromussa, a tort, purple fuzzy and a BTA. Would like clams to live in the tank, 2 died under the 150W's. <Not enough 'usable' light with the 20K.> I'm having a big problem deciding. Thanks for your patience. Also, no heat issues right now, but will I have serious heat issues if I do go with the 250's, <Quite possible.> Thanks <You will realize a large increase in light your corals/clams can use with the simple switch to a lower wattage bulb. Two 250W would be overkill in my opinion considering it is a three foot tank and the lights will overlap quite a bit. The 175W would be fine, but again different bulbs in the 150W fixture would be the way to go considering the lighting will overlap. Check out the link below, noting the difference in PPFD (Photosynthetic Photon Flux Density; what your corals use) between the 10K and 20K bulbs. Welcome, hope this helps you decide, Scott V.>

Using Heater Controller For Controlling Halides 12/26/07 Hi Crew, <Hi Tom> We're leaving for a few days of vacation <Take me with you:)> and are trying to eliminate some of the many possible failure points in our 130G reef tank. One worry is that the chiller could fail and allow the halides to cook the tank. Have you tried using a heater controller to cut power to the halides if the temperature gets too high, like this one: http://www.championlighting.com/product.php?productid=21402&cat=389&bestseller Seems like it ought to work. I searched WWM for "halide" and "controller" but didn't find any similar references. <This product is not intended to do this and I doubt very much if it would provide the inrush current needed to start the lamps. Other problems can/will occur as well. Be safe and do not use this product for that intention, you may be looking for a home when you return.> Thanks, <You're welcome. James (Salty Dog)> Tom

MH Lighting, Acrylic Tank, Very Low Canopy...Not The Best Recipe -- 10/18/07 Greetings, <<Morning>> I've found a lot of useful information on your website, but after reading countless FAQs, I still can't come to a decision on lighting for my tank. <<Oh?>> I'm currently in the process of setting up a 400 gallon reef tank (96"L x 30"W x 36"H). <<Cool!...love big reef tanks...have a 375 myself>> I've got just about everything I need except for the lighting. <<Okay>> It's an acrylic Tenecor tank with two 25" x 15" top openings on both sides, with 21" between openings and 13.5" on either side length wise. <<Mine too is a Tenecor built tank, though I had them 'customize' mine with three openings in the top versus two to make 'lighting' the reef easier...as you are no doubt discovering with that 21'-wide center brace. In retrospect, I wish I had spent a bit more money and had the top thickened and the bracing/perimeter reduced...but I digress...>> I've got about 275 pounds of live rock and a few fish, and the tank has been running for about three months now. I'm currently using a 36" Coralife Aqualight Pro out of my old setup, which has 1x250W HQI lamp, 2x65W CF lamps, and 2x1-watt LEDs. My problem with the new setup is the canopy. I've only got 6" from the top of the acrylic to the bottom of the canopy, which doesn't give me a lot of room. <<Mmm, indeed...and if you are planning to install MH lighting this will be too close and enclosed in my opinion (bulbs will be mere inches from the acrylic)...serious potential for softening the acrylic and causing a catastrophic failure of the tank. I have seen 250w MH lamps placed within 4-inches of ¾' acrylic soften it to the point where a 14'-wide brace would flex with the push of a finger...and these lamps were not 'confined' in a canopy. Even if you position the bulbs over the openings on your tank, I think the confines of your very low canopy will hold too much heat. I'm doubtful fans will even be of much help considering the proximity of the bulbs and the containment of the hood>> On top of that, both top sides of the canopy open up independently, so I'm not sure how I could hang a fixture over an opening. <<Not sure I follow this...>> (The openings have acrylic covers, but everything I've read thus far says that the MH lights aren't as efficient shining through the acrylic.) <<Is not a matter of efficiency...'clean' acrylic will allow about 95% light transmission regardless of the light source (and for what it's worth...regarding reef systems, metal halide gives the most 'bang for the buck'...in my opinion). But you don't want to leave those covers on anyway as they trap heat, reduce evaporative cooling, and, depending on how your system is configured (e.g. - sump/no sump), can prevent adequate gas exchange>> The Coralife light is currently resting on modified legs, with the lights just over 2" away from the top of the acrylic. <<Dangerous...in my opinion>> Any help that you could give me would be greatly appreciated! Great work on the site, and if I left anything out, please let me know. Thanks! Heavy D <<Well Heavy D, your options as I see it are these... You can use the current canopy but with a 'cooler running' light source light standard-wattage fluorescent bulbs (will limit stocking organisms with 'high' light requirements). These standard-wattage bulbs will still need good ventilation to prevent excessive heat buildup in the canopy. You could consider HO (T5) or VHO fluorescent tubes, but these get 'quite hot' and again, the confines of this low built canopy may prove too much... Another option is to abandon this canopy and build/have built one that is 'designed' for use with the high-intensity metal halide lighting... A third option is to abandon using a canopy altogether and opt for open suspended lighting such as metal halide pendant fixtures. You don't state what biotopic representation/type of reef tank you plan to keep...but if you really want to utilize the high heat producing lighting usually associated re...it just doesn't seem like the canopy you have is going to work with this acrylic tank. Please write back to discuss further if you wish. Regards, EricR>>

Re: MH Lighting, Acrylic Tank, Very Low Canopy...Not The Best Recipe - 10/19/07 Thank you for the quick reply. <<Quite welcome>> Your name is a good one, but to set the record straight, it seems that you've spelled it incorrectly. I believe it's spelled with a "K". <<Ha!...perspectives!>> To give you a better idea of what I'm working with, I've enclosed a few pictures. <<Thanks much for this>> Picture 1 is my setup as it sits, without the canopy. <<Okay>> Picture 2 is where my Coralife MH light sits right now, on the modified legs. Not too far above the acrylic... It's 3/4" thick, and I haven't had a problem yet, but I'm pretty sure you have a lot more experience with this kind of thing than I do. <<It may well be fine>> Picture 3 is just an overhead view of the top of the aquarium. <<Mmm, not much 'open space' for sure'¦the bane of the 'stock' acrylic tank. Obviously whoever designs these has never had to 'work' in one of these tanks'¦>> I too wish I would have had something a little more "custom" built, as this was a standard Tenecor tank. <<Indeed>> They built the cabinet and the canopy as well. <<I see>> When I ordered it, I didn't really have the intention of building a dedicated reef tank. <<Oh?>> After reading up on the subject and seeing all kinds of pictures, I decided after the fact that it was something I wanted to do. <<Ahhh'¦the little slice of ocean in your living room'¦ Can be/is very addictive'¦ As said by this 30+ year marine hobbyist who became a 'reef-addict' about 17 years ago now'¦so I do understand the allure>> Probably not the smartest thing, but it is what it is. <<Yup>> The cabinet is too small to house my sump/refugium, (that's all in the crawl space) and the canopy is apparently not tall enough to house MH lights. <<A common problem all around'¦ I do wish manufacturers would design these items with more of an eye toward housing the necessary support systems>> Again, I wish I had something a little different. <<Mmm, how's that saying go'¦ Hindsight is 'always' 20-20'¦>> As far as the canopy goes, I'd like to use it with my current setup, as taking it off doesn't leave the tank near as aesthetically pleasing. <<Indeed>> It's in a dining /living room area, and I like the way it looks with the canopy on. <<Understandable>> Picture 4 is the canopy, and that's what I meant when I said that both top sides of the canopy open up. That's my only way to get inside the tank, and I don't know how I would suspend something underneath them. Not that 6" gives me any room to suspend something... <<Ugh'¦ I see what you mean. Looks like 36' fluorescent bulbs mounted to each door will be your best option>> When it comes to species, I really haven't decided what I'd like to keep yet. <<This will determine your lighting needs>> Any recommendations that you have would be greatly appreciated. <<I suggest you first research and decide on a specific biotope or niche of the reef you would like to replicate. Stocking organisms from the same ocean and reef habitat/zone/niche can mean much toward long term success>> Again, I don't really want to get rid of the canopy, so if I need a light source that's not going to be bright enough for my setup, I guess I'll have to deal with it. <<If you can get some air flowing through the canopy'¦T5 HO lighting is worth a try. I doubt you can fit the 4-foot 54w bulbs and end caps on those door panels, so you will have to go with the 3-foot 39w bulbs. I figure you can fit about eight bulbs or more (w/reflectors) per door panel on this 36' deep (wide) tank. The T5s are very nice technology'¦I have even seen some beautiful European SPS tanks lighted with these bulbs, so'¦the possibilities/choices for your reef may be broader than you think>> It's been fish only so far, and by the sounds of things, it may have to stay that way. <<Maybe not'¦ I would feel better if the canopy were taller to allow better heat dissipation along with positioning of bulbs (metal halide) further away from the acrylic. But if you can get enough air moving through the canopy through the installation of some fans, the T5 lighting could work out fine>> One more quick question for my current setup... <<Sure>> I've been getting a lot of algae on the front glass. If you look in from the side, you can see that it follows the pattern of where the light shines. <<Typical>> Is this just a case of having the lights on too long during the day? They're on for about 12 hours right now. <<Nope, this lighting period is fine. The algae is likely a result of the newness of this tank (hasn't found/reached its 'balance' yet)>> The light is so bright at night that I've had a few neighbors ask if I currently have a 1.)Botanical garden or 2.)A tanning bed in my living room. <<Hee-hee! When I was building/installing my system (in-wall), and before I had the lighting enclosed, my neighbors and visitors to the house thought I must be growing 'Pot' in the living room because the light was so bright!>> Should I cut the lights back to 9 or 10 hours to help with the algae? <<Not my opinion>> I can only assume this will get worse if I add more lights. <<Unless something is amiss with your filtration/feeding/stocking levels, or you're not filtering your tap water'¦this will likely pass>> Thanks again! Heavy D (a.k.a. Erik) <<Always welcome'¦do let me know if I can assist further. Eric Russell>>

Metal Halide Lighting... mostly  10/16/07 Hey, So I have a few quick questions: I have a 36" 442w metal halide fixture (2-96w blue actinic, 1-250w 15k Halide), and it is leg mounted above my aquarium, ~6" above the water. My tank is a 65 gal tank, 2ft deep and 3ft wide. Should I worry about this being too much light for my corals? <... depends on what you mean by "corals" and what they've been kept "under"...> I currently have a waving hand xenia situated about 20" below the halide, a frogspawn in the far corner on the bottom, some green star polyps in the opposite corner of the frogspawn and a few mushrooms about halfway down the rockwork in the middle of the tank. All seem to be doing very well, the mushrooms have almost doubled in size in two weeks, the green stars open daily and the waving hands have 6 new sprouts. The only one that is a little off is the frogspawn, which originally had 3 branches, but the smallest one (which was tiny) seems to have died off, while the other two are looking all right and opening everyday. <Is something other than lighting at play here...> Should I worry about the small branch dying off? <Maybe> Also, unfortunately, the MH bulb is right above the center brace of the tank. <I'd move the light slightly to one side or t'other> I have had it running for over 3 months now, and have seen no signs of melting yet, but have read some horror stories of what can happen when they melt. Should I do anything precautionary for this? I was considering placing a few acrylic braces across the tank evenly spaced, but distanced from the MH bulb. I would probably have to shape them something like this: l__________l but inverted, and make it large enough to slip around the outside rim of the tank, then cement into place. Thanks for this website, I honestly would have probably either given up or wasted alot <No such word...> more time and money than I already have without, you guys are great! Thanks, Dan <Mmm, please read here: http://www.wetwebmedia.com/marine/inverts/index.htm re: Euphylliid Health, Cnidarian Compatibility... Bob Fenner>

Metal Halide Fixture Choices vs. Over-Heating Issues -- 08/10/07 I have looked through the articles posted and can't find an answer to my question so here it is. I'm looking for MH for my 240G set up. The tank is 72x30x25. I am planning on 3x250w MH supplemented with T5's. <<Okay>> My question is what is the best type of lighting to go for? <<Mmm...what is it/what effect do you wish to achieve?>> I'm putting these fixtures in a canopy. I was very keen on the Lumenmax3, but fear they might have a heat build up. <<This is a very nice reflector/pendant, and no more likely to cause heat problems than any other...and heat 'will' be an issue in this canopy regardless of the lighting fixture>> What I like about them is that they are compact and have the UV glass shield. <<I can think of some others with the same aspects...but this pendant is a fine choice>> I have also read reports on the vented Lumenarcs, do you need UV glass under them if they are in a canopy? ( I guess they would still be dangerous when you open the hood). <<Indeed you do, any time you are using the 'double-ended' bulb fixtures...and the hazards of not doing so extend to your livestock as well as to you and your family>> I have also got a fairly large (1300 cfm) <fan> that I was going to suck hot air out and have fresh air supplied by the A/C ductwork (or outside air in the winter). <<Sounds like a good plan>> I'm still a little confused as to what would be the best setup with regards to minimizing heat build up. <<I think what you have outlined should be fine, though you may have to experiment with the size/number of fans and vents to handle the overheating issues>> Thanks in advance for your help. Olly <<Happy to assist. EricR>>

Re: Metal Halide Fixture Choices vs. Over-Heating Issues - 08/11/07 Thanks I appreciate your reply. <<Quite welcome>> What would be the minimum distance from the bottom of the reflector to the water? <<Whatever places the 'bulb' within a general range of about 8' -- 12' from the water's surface>> I have a 12" canopy, and say the water will be about 1" from the top of the tank, and that most fixtures are between 6" and 8" that will only give me about 5" -7" of clearance. Is that sufficient? <<Considering the bulb will be a bit higher within the fixture, yes, this will likely be fine>> Thanks again, Oliver R Oakley, PhD <<Happy to help, Eric Russell>>

Glass lid needed with metal halide?  -- 07/26/07 I've found so much information searching on your FAQS on the web. <excellent> I wasn't able to find a answer with the same equipment as in my tank. I ordered a Sun Pod 2x250w 14k MH fixture for my 90 gallon reef and it will be mounted 12 inches above my glass lid. Since I plan to keep SPS corals in my aquarium, will I need to remove my glass lid in order to give enough light to the corals? <The glass lid will, to some extent, decrease the amount of light getting to your corals. But how much light it will impede depends a lot on how clean and dry you keep it. Lids have a way of getting wet, salty, and/or dirty pretty fast.> As for the heat issue, I have a chiller set at 76 degrees. <You'll definitely need that chiller with the glass lids and metal halides.> Which can be adjusted as needed when the fixture arrives so I don't think I would need to remove the glass lid for the heat issue. If you guys/gals think I should remove my glass lid, I'm very worried about my fish jumping out. Any way to prevent this? <Since you have a chiller, the only concerns left with the lids are going to be of gas exchange and the lids getting wet, salt, and/or dirty. If you can manage to get good aeration even with the lids, and if you can keep the lids clean and dry, then you should be ok. But if all that becomes too difficult, there are a few other ways of keeping fish from jumping out. If the fish aren't really small, eggcrate should work. If not eggcrate, there are other similar type plastic grates you can get at hardware stores that might work.> Thanks so much again for all of your support! <No problem> Peter <Best, Sara>

Lighting/Heating Question (MH lighting and hot temps) - 6/1/07 Hi Crew! <Hey WS.> I've searched your site and can't find the help I'm looking for...so I decided to write you instead. <Okay.> First off...you guys/gals have helped me tremendously every step of the way from my first 55gal to my current setup 210gal system. <Awesome.> My family and friends love our aquarium. My family rarely watches TV anymore. Good thing we didn't get the plasma screen TV instead. <Oh don't tell anyone I got both...lol.> Here's my setup... 210 gal, going to be mixed reef system. 250lbs LR Current livestock is... 9" Volitans Lionfish 1" Yellowtail Damsel 4" Emperor Angel 5" Harlequin Tusk 4" Sohal Tang 1 Devils hand Leather 1 Colt Coral Large Zoo colony 1 Open Brain Coral All are doing great! <Cool.> I currently use an Aquamedic Oceanlight T5/MH combo. 3x250 watt MH, and 4x39watt T5 actinics. This is a relatively new light (1 month), and I'm having trouble maintaining a steady temp. I run the T5's for 12 hrs, the middle 1x250 watt MH for 8 hrs, <Too long for the MH, you really don't need much longer than 3 or 4 hours, especially for what you have.> and the outer 2x250 watt MH for 4 hrs. <That is okay.> I don't want to get a chiller (my electric bill is too high already), and I'm just not eager to part with my money. <I understand.> With this lighting schedule my temp in the morning is 79.5-80 degrees, and by 2pm it's 80.5 - 81 degrees. I haven't been able to run my outer 2MH's for the full 4 hrs (from 12 - 4pm) that I wanted due to the temp increase. I usually end up shutting them off after about 2hrs of use (which I don't mind doing). <What about cheap'o computer fans on a timer, can help tremendously and is very cheap.> I planned on getting 2-3 pc.s of LPSs or SPS (not sure what kinds, still researching). I know my livestock might not be reef safe, but so far so good. <As long as you know the risks.> Finally, my question... <Okay.> Since my 1x250watt MH is on for 8hrs, do you think these corals will do well under the lit part of tank? I was thinking frogspawn, Montipora Plate Coral, and maybe an Acropora frag? <Zooxanthellae hosting organisms really only need 3-4 hours of direct (MH) lighting, the rest can be supplemental fluorescent lighting (The T-5's).> Thanks again. <Anytime.> WS <Adam J.>

Re: Lighting/Heating Question (MH lighting and hot temps)  - 6/7/07 Thanks Adam <Anytime.> Is it harmful to corals soft and hard, to have the MH on for 8 hrs? <I wouldn't leave all of them on that long but if you want to leave the lower wattage, center one, out of three on for an extended period...and I assume this is for aesthetics...ten I don't see an issue. Keep in mind though that it may/will contribute to algae growth.> I like the difference in colors with the T5's on and 1 MH on. It looks cool. <I bet.> Thanks again. <Anytime.> Wayne <AJ.> MH Distance from the water?   3/21/07 <Greetings!  Mich here.> I have an Outer Orbit all-in-one system. 550 Watts. 2- 150 Watt 10K metal Halide, 4 54 Watt Actinics, and lunars. How many inches should it be from the water to get proper lighting, but minimize evaporation and heat? <Generally 4-12 inches, in you case, 8-10 inches would probably be best.> Thanks. <Welcome.  -Mich> PS - I do not run the Halide's all day to save electric cost.   <Hopefully is at least 8 hours, 12 would be better.>

Lighting...Metal Halide Placement 1/9/07 I own a 180 gallon tank with a retrofit kit attached to the canopy hood cover. That light has 3 -250 watt 15k bulbs and 2 VHO bulbs. I also have 2 VHO lamps near the water, not attached to the canopy. The light looks fine but when I take pictures their not as good as the LFS's  tank when I take photos of theirs, and they have a 180 gallon also with the same kind of light wattage but no canopy and their lights sit 7 inches above the water. My question is what is the appropriate height for metal halides with a wooden canopy. I think it said  9-11 inches on your site I believe, but did not say if it was with a canopy. what should I do? If it's too close will it boil the tank. What's the right height for intensity and not boiling the tank? <Harry, the canopy lights should be fine providing you have a large enough (cfm) fan to exhaust the heat emitted from them.  The hood will require an inlet and outlet for the fan to operate properly.  As for the VHO's, why run them?  Your halide system alone is more than enough for your tank.  The photo problem; I'll bet the Kelvin temperature is different on the LFS lamps than is yours. His indirect lighting may be much brighter also.  If your camera has the capability to select white balance, change this to the different settings available, and I think you will find something to your liking here.  Experiment with it.> Harry <James (Salty Dog)>

Metal Halide Bulb Placement (Parallel? or Perpendicular?) - 04/30/06 Hello wet web, <<Hiya Mike!>> Let me lay out what system I have really quick to give you a better idea of what we are working with. <<Thank you>> I have a 100 gallon SeaClear System-II aquarium.  One main pump, two powerheads and a separate pump for the chiller.  2x175watt MH and a 1/4 JBJ Arctica chiller.  I have read through your FAQ's but have not gotten a definite answer. <<Ok>> My question is, is a 2-degree temperature fluctuation too much for my fish and coral? <<Not usually, no>> The chiller cools from 78.5 to 76.5 in about 20-25min and it will do this about 2-3 times per day depending on how hot the day is. <<Mmm...that's a pretty rapid drop>> Is this how this chiller is supposed to work? <<Yep>> If not, what is an acceptable range for a chiller to chill? <<?>> Do I have the settings on wrong? <<Not "wrong" per se, but could be "improved".  Does your chiller allow you to adjust the temperature differential?  You should be able to set the differential (the number of "degrees" the water temp is allowed to rise from your "set" temperature before the chiller kicks on), adjust this to 1-degree of differential to reduce the size of the temperature drop>> I have the low setting at 76.5 and the high setting at 78.5 degrees. <<Ahh!>> What am I doing wrong? <<Nothing really, all is probably fine unless you are seeing signs of stress in your tank inhabitants.  But for a more "stable" environment, you can either increase your "low" setting or decrease your "high" setting>> Also, does it matter if I mount my Halides perpendicular or parallel to the front of my tank? <<Most folks opt for "parallel", but if you have adequate light spread/coverage I don't see what difference it really makes>> Keep in mind that I have a rectangular 5' acrylic tank. <<I too have an acrylic tank...my halides are mounted parallel>> I was thinking of using the PFO parallel reflector that can also hold two power compacts or I can also use the PFO parabolic reflector which places the bulbs perpendicular to the front of the tank.  Do you guys know if these reflectors are any good? <<I use PFO reflectors, I think they are a fine product/value>> The reason I'm asking is because I heard that if you place Halides perpendicular to the front of a tank it can warp the front of it. <<Huh?! How?>> Is this true? <<Not that I've ever heard>> What can happen to my tank? <<Whether your bulbs are positioned parallel or perpendicular should make no difference in this respect>> The help is much appreciated, Mike <<Mike, considering the dimensions of your tank I think a parallel configuration would be optimal...but if you' rather go perpendicular I don't see any great problems with this either.  Regards, Eric Russell>>

90 gallon Reef MH question, heat   9/5/06 Bob,     I have read a lot of your articles on WWM about the  Metal Halides and everything else.  I currently have a 90 gallon all glass  aquarium with a corner overflow.  I'm currently using a Aqualight Plus  Fixture contain 2 10k whites and 2 actinics all being 96 watts with the standard  wooden canopy above the lighting and the tank.  The tank without the use of  a heater stays around 77-78 degrees.  I'm playing with the idea of getting  the New Outer Orbit lighting system that contains 2 150w 10k  HQI MH and 2  130 watt PC Actinics.  With the tank being a taller tank and liking the  shimmering effect of the MH i wanted to know if there was a way to include the  canopy at least on the outside without worrying about the heat issue. <Fans... a chiller...> I  don't mind having an open top canopy but i would like to at least have some type  of a canopy so that i don't see the light fixture.  I was thinking about  installing two fans in the back on the canopy to blow the air out from under the  lights as well as drilling some holes on the outside of the canopy to allow air  flow thru the fixture itself that does contain an 3.5 inch fan always. <Better to blow in and out...>   I  just don't really like the fact going somewhere and seeing the lighting fixture  and the light peeking thru the sides between the light and the top of the  canopy, but i do understand that MH put out a lot of heat but i wasn't sure if  these HQI lights with the new design of ballast put out else heat.  But my  main issues is being able to put the light system on the tank without it being  too much light for the corals, LPS, Calms, SPS and zoos and polyps. <Won't be here>   And  having some type of a canopy around the sides so the tank looks complete like a  piece of furniture not just a tank please let me know Thank you Drew <Can be done... will likely need a chiller. Bob Fenner>

Re: 90 gallon Reef MH question.  9/6/06 With the MH being about 7 to 8 inches off of the water is this ok, or is it going to cause the light to be too intense for the tank. <Need to elevate this high or higher for light distribution and safety reasons... see the manufacturer's recommendations re>   Do you believe that with fans I can keep it cool or more than likely i will have to have a chiller, which i really don't want to purchase at all. Drew <More than likely the chiller will be needed if using 250 watt units or higher. Bob Fenner>

T5 or MH, Heat Issue...   9/2/06 Hello Crew,     I'm upgrading my 100 gallon tank into a reef tank. Currently I'm planning on removing my closed canopy and replacing it with an open lighting fixture. I've set my mind on either Metal Halide or HO fluorescent T5 lighting.     The thing is, I don't know which lighting will be better for my setup. My tank dimensions are 58" wide and 18" deep. I would like to keep Bubble-Tipped Anemones and Tridacnid Clams (I would place the clam at the bottom of the tank). My preference in Corals is still not clear, but I would like to be open to a wide range of possibilities.     I've read through your FAQs that Clams prefer MH (and so do I, due to the pleasing shimmering effect), but heat is an issue to me. My room temperature is 25 C, but my tank is around 27 C and I think it's mainly due to the trapped heat in the closed canopy (with three 40 watt fluorescent lamps, will remove soon). I'm also adding more powerful powerheads that will add up to the heat. I'm not sure if T5's will provide enough lighting for the intended inhabitants while emitting low heat, and need your inquiry. Thank you. Have a nice day. Mohammad <<Mohammad:  While there are some people who like T5's the vast majority of people that have anemones and clams (including me) have MH lighting.  If your canopy is open, I don't thing the MH lighting will significantly increase your temperature.  Some day, we may be able to light our tanks with LED's; but, the technology is still being tested.  Best of luck, Roy>> Cube? MH, heat concern 7/16/05 I'm planning a  26"X26"X23"  tank.  My wish is for single 150 watt HQI  to support a FOWLR  system.  The internal overflow box spans the back, has three 1" bulkheads,  and  two pairs of  3/4" , on the bottom of the tank.  (Two for return, and two for a possible future closed loop.) <The return/lines you may well want to raise up to prevent back-siphoning in the event of a power/pump failure> The Iwaki MD-40RX, for a SCWD only return,  The sump's water depth will be below  9" to accommodate a Aqua-C EV-120,  and incorporates a  25 gallon refugium.   I would appreciate any advice, or to know if I'm on the right track, here in Taiwan.  Thank you, for your invaluable service.  I apologize if I have been unclear. -Ryan <You may have heat issues with the size, shape of the main tank, volume of water. Bob Fenner>

Too much light? MHs 8/9/05 Hello crew, I have a 125g (72Lx18Wx22H) salt water tank w/fish only. I plan on a reef tank w/light loving corals. I bought a used dual 400w MH kit at a great price. I know this is too many watts for the depth of the tank, but I couldn't resist for the price. So can you please tell me what I can do to make it work. I read that you can use window screen in layers but wouldn't this melt? <If it's too close, yes> Can I move the lights higher than normal? <Yes> The tank has two plastic braces at the top, how hot will these get, and can I cover them with a heat shield type of cover. Thank you for any info.   <No heat shield... but you want to keep at least a foot of space between, and never heat them more than you can stand to place your hand on... You might look into means to "turn down" (through electronics) your 400 watt units to lower wattage (will save you a bundle on electricity costs, as well as not having to walk around the house with sunglasses on...). Contact the larger lighting outfits... maybe Perry Tishgart at Champion... re this possibility. Bob Fenner>

Metal Halide (UV) Shielding - 10/13/05 Hello all and thanks ahead of time, <<Howdy>> Am somewhat confused at why MH spotlight type pendants are able to be shielded in pendant and HQI fixtures are able to be shielded in pendant, but MH hoods and canopy lights cannot except for a lid on top of aquarium at some distance from bulb. <<Not sure where you got this info, but most any manufactured light fixture, whether pendant or otherwise, mogul or DE, will come with some type (plastic/glass) lens (shield) attached to the fixture. I wonder if you might be referring to the argument on "whether or not" to shield MH bulbs? There has been some debate on this, and many folks choose to shield HQI/DE bulbs because they lack the outer glass envelope of a mogul bulb. You can argue that the sun has no such shield, and there are writings stating that much of the colorful pigments seen in some corals are proteins produced to "shield" the corals from the sun's UV...but most folks will err on the side of caution and shield their HQI/DE MH bulbs. I currently utilize mogul bulbs, and I don't shield them.>> Are HQI / mogul type spot pendants and fixtures less hot than canopy / hood MH lights? <<Not as a rule...depends on design, wattage, presence of electric fans...>> Just finished Mr. Calfo's Book of Coral Propagation. Rarely is a book so informative and fun/entertaining at the same time!!! <<am much in agreement>> Bravo A.C. and thank you all, Peter Puzzled in Lakewood, Ca <<Regards, EricR>>

Re: Metal Halide (UV) Shielding - Follow-up 10/15/05 Thanks Eric!!! <<Most welcome>> To follow up then, the MH mogul type aluminum hoods with a fan on each end can be shielded right there on the hood, similar to a fluorescent fixture? <<Sure...will likely come with some type of splash guard which also functions as a UV shield. Some materials (treated) are better than others, but any glass or plastic lens/splash guard will filter "some" UV.>> If so then is it placed directly on tank top, suspended, mounted or any of the above? <<Is up to you...but I don't recommend placing (resting) the light fixture directly on the tank top. Allow a couple inches for air circulation...some fixtures come with little "feet" for this purpose.>> And for retro fixtures attached to wooden canopy top, can the bulb be shielded at the fixture instead of having to cover the tank with a sheet of glass/acrylic? <<This can be done by attaching to the hood, yes. But if you go with mogul bulbs I don't see the need myself.>> I've never seen moguls shielded in a retro fixture for some reason. I am a safety consultant by profession and it makes me cringe to see those exposed bare bulbs above the water. It gives me a "0" comfort level. <<Little to be concerned with here, really...the mogul bulbs are already shielded by the outer glass envelope. The biggest danger in my opinion is breakage caused by splash on the bulb, and even this is minimal. Most folks are trying to get all they can out of their lighting, and adding a "shield" only reduces intensity/PAR.>> Just like all the tanks I see set up relying on check valves to prevent back siphoning. Arggggh! Or single hole overflows!!! etc. <<agreed>> Please indulge my "safety first" nature with my above concerns regarding the MH's. <<No worries mate, you have to do what makes you comfortable. You can still provide adequate lighting for your wet pets with a little planning.>> THANK YOU and BE SAFE Peter Lakewood, Ca <<Always welcome, EricR>>

More On MH Lighting Shielding - 11/18/05 Thanks Eric!! Getting clearer. One more follow though, please. I have read on your site that by mounting MH too close to the tank top this has caused the glass to crack/acrylic to melt.  If true, what material is used to shield bulbs in fixtures (like HQIs for instance that does not crack/melt so close to bulb?? <<Tempered/treated glass...adequate air flow around same.>> And why does tank brace crack, but not shield glass? <<Not usually tempered/treated to withstand extreme heat.  Keep in mind too, the glass used to shield the bulbs is not under the same stresses the tank brace is (i.e. - bracing together a tank full of heavy water).  As for plastic, some of the bell-type pendants use plastic/acrylic shields.  These don't "melt" due to the air flow around the fixture, but, place it too close to the tank top and restrict that air flow...you get the picture.  Ideally, you won't have a cover on the tank (reef tanks especially, need to "breathe"), and most fixtures with multiple bulbs are designed to place them on either side of a center-braced tank.>> Sorry for follow ups, just want to be clear on this. Thank you Peter <<Follow-ups are no problem my friend, EricR>>

Aquatinics MH Hoods - 10/15/05 Hi Eric, PS--please check this Aquactinics.com site for MH hoods that can be set right on top of tank and contribute almost zero heat. What do you think, please? Skeptical but intrigued in Lakewood Peter <<Mmm, might be fine but like you...am skeptical. I would still conspire to raise the fixture by an inch or two...perhaps fashion some "legs" from acrylic for this purpose. I'm guessing you noticed the UV splash shield? <G> EricR>>

MH light height  1/8/06 Hello all,   <Hello.> I hope the holiday treated you all fine ! <No complaints here, thank you for asking.> Just a quickie, <Sure.> have a 55 Gal Mixed salt water tank that's around 20in Deep from water surface to sand bed,  I have 2x250w 14,000k Halides running 10hrs and 2xActinic running 12hrs.  The lights themselves are rated for a tank up to 36in deep and the manufacturer recommends a minimum distance of 8in from the waters surface, however the lights are causing a temperature fluctuation of around 4 deg (79 to 83 deg) over the 10hrs. <That's not cool.> Due to the main tank being located in our family room I am unwilling to have a noisy fan running for 8hrs a day at this time and a chiller isn't an option. <X2, 3' computer fans won't, can't, even be heard over the noise of the average aquarium pump.>   With the lights being really more powerful than the depth of tank I have require at this time.   Would increasing the distance to around 12-15in to lower the heat transfer from light to water, have adverse effects on my Clams & softies (leathers, mushrooms, Xenia). <This distance (height) should be fine for your tank.> Happy new Year to you all from Wiltshire in the UK. <And a happy new year from SoCal, Adam J.> MH v Fluorescents, power consumption   1/10/06 Hi WWM Crew, <Hello Steve> I was reading one of the FAQ's when I came across a minor mistake and thought I would correct it. The WWM crew was asked if 150 watts of MH consumed the same amount of power as 150 watts of fluorescents and the answer was yes a watt equals a watt which is true but watts = amps x volts and a 150 watt MH light will consume more power or energy whilst supplying the same amount of watts, i.e.. more amps. The extra power is dissipated as heat from the ballast. <This particular answer may be dated.  The efficiency (power factor) of a system depends on the ballast.  Electronically regulated ballasts will be more efficient than a tar ballast and so on. This will also relate to light intensity somewhat.  On a 48" tank, two 150 watt HQI's are going to be more effective than 400 watts of fluorescents and generate less heat into the tank.  So now we are looking at light intensity versus wattage being used.  More than just watt for watt has to be considered here.> I hope this helps, regards, Steve. <I hope this helps also. James (Salty Dog)>

HQI bulb   1/18/06 Hello, <Hello Orestes> I am starting a 60 gallon reef tank and have a retrofit kit for two 65 watt actinics and 1 150 watt HQI double ended bulb. The lights sit about 5 inches from the surface of the water and my question is how should I place the bulbs so that I do not have any problems with the heat of the HQI affecting the actinics. Oh, I also have two 3" fans from Coralife one blowing cool air in and the other sucking hot air out. <The heat from the HQI will have no effect on the PC's.  James (Salty Dog)> <<I have a differing opinion. Would situate the fluorescents at a distance that is comfortable to your touch... RMF>> Thank You. <You're welcome> Orestes Halides? Hello, I've reading you site and it is great!      I have a 55 gallon aquarium.  Currently I have a Tunze pump that has the flow restrictor pointing to the surface.  There is quite a bit of surface agitation which is preventing the power compacts from penetrating too far into the aquarium.  I know because when I turn it off it becomes quite a bit brighter in the aquarium.  So, I am thinking about purchasing two 175 W metal Halides and installing fans in the canopy.  << Excellent idea. >> I live in San Francisco where it is cool most of the time but in the summer in can become hot enough to be a problem. << My diving partner lives in San Francisco. >> Do I need a chiller? << Nope, a few fans and opening the back of the canopy will do it.  Having air conditioning in your house is also very helpful. >> Also, are metal halides the way to go.  I currently have some brain corals and clams and would like to grow SPS corals. << Without a doubt.  I would definitely go that route.  >> Thanks, -Brent <<  Blundell  >> Lighting... Hi...I have a 48in. X 18in. X 18in. reef aquarium. I am using 4 fluorescent lights. I am thinking of using metal halides. If I were to use metal halides, must I use a chiller,,,?? My aquarium is between 29 - 27 degree Celsius with 3 fans on. Without the fan, it will be around 30 - 32 degree Celsius...when using metal halides, how high should I place it above the water surface (planning to use a 150 watt metal halides)...?? Thanks... >>>I don't use a chiller, but every tank/room combination is different. With 150 watt halides, you should be fine without a chiller though. Keep the fixture 35cm above the water or so. Cheers Jim<<<

Lighting... dangers of MH use Good evening.  I have looked on the wetwebmedia website and have found some information on this topic but not any detailed discussion.  I have a tank that is 120 gallons (4 feet x 2 feet x 2 feet).  I have an enclosed wood canopy with HQI metal halide lights (2x250) in housings with clear acrylic (glass? not sure which, they are the standard HQI housings and covers that are rectangular) covers and two power compact actinic bulbs without shielding.   To reduce the heat in the tank I usually use two small half inch blocks to slightly raise the top of the canopy so that there is a gap for air to escape. <Mmm, would be better to drill some ports... chimneys if you will for passive venting... better still to blow air in/out via fans>   The tank is kept in our living room with the lights running for approximately 9.5 hours per day.  I also have a young child.  My question is regarding any danger that is posed from the metal halides and, in particular, UV-radiation. <Modern aquarium metal halides present little danger from UV> Am I potentially introducing a health risk into our home, particularly in terms of having a young child in the house?  Any input on this would be much appreciated.  I have seen some articles on this topic but no definitive conclusions. Thanks. - Brian <I do share your concern... particularly re heat issues, the possibility (very real) of fire. Do please look into drilling those vent holes and the possibility of adding fans... check that acrylic anywhere near these lamps is not discoloring, crazing from heat... the flashpoint of this material is not far from this... Bob Fenner>

Re: MH Lighting danger Thanks very much for the response.  One important item I forgot to mention is that I prop the canopy in the front by a half inch because I have two four inch fans on the back of the tank that draw air into the tank and the gap allows the air to escape in the front, thus keeping the lights cooler. <Ahh... better to just cut some holes (like with a hole-saw and a drill motor) and affix some screens over... for intakes> Anyway, my primary concern was if the metal halides pose any health threats, particularly to very young children.  I was particularly concerned with UV and if there are any other concerns.  I had mentioned the propping of the lid because this lets a little bit of additional light into the room. Thanks. - Birna <Yes, I understood, understand the UV to be the primary concern. To be more specific, for the sake of concern re ultraviolet damage to eyes, modern fixtures (all supplied sans such filters) do NOT pose a threat... and older ones will come supplied with such transparent screens. Modern MH/HQI lamps have such radiation shielding built in to their construction/glass. Bob Fenner>

Re: MH Lighting danger, fans Great.  So it sounds like my fear of medical damage from UV appears to be unwarranted with the modern fixtures/bulbs (be they vision damage, developmental damage, health risk, etc.).  I guess if there was a risk they would not be selling these items(?). <Mmm, I would NOT go this far> Sorry, last question on the fans.  Do you think that I can move the fans to the front of the canopy with some spacers between the fans and the wood and then close the front of the canopy (basically blowing the air out the back), or would this likely not work since I would not be drawing in any cooler air? <I would NOT place the fans or vents in the front... annoying light, sound... affix them to the back, sides, top... Bob Fenner> Thanks. - Brian

Re: MH Lighting Thanks very much for your advice and for the great website; it has provided me with invaluable assistance in choosing appropriate aquarium inhabitants. I guess I was pushing it a bit in my assumption on the ethical composition of the lighting industry, but it sounds like the health risk that I was concerned with for the metal halide lighting is not existent.  That is a relief.  On a side note, I took a closer look at my lights and the covers on my halides are glass and not acrylic. Thanks again. - Brian <... the glass will filter the UV. Have you read the collective FAQs on Metal Halide use on marine aquariums? Here: http://www.wetwebmedia.com/marine/setup/lighting/mhmarfaqs.htm and the links above. Bob Fenner>

Halide upgrade and center brace Dear Crew I have read somewhere on your website that its dangerous to have halides on an aquarium with a centre brace? My tank is a 72 inch x18 x 24 high. I am upgrading my VHOs to an arcadia pendant style MH setup (series 3). There will be a new open top hood placed on the top of the tank. My question is why is there a problem with halides and a centre brace?  <Jim, I think what is implied here is that a halide directly over the center brace (most braces are plastic) will cause the brace to soften and allow the tank to bow. If you are going to use just two 250/400 watt (whatever) halides adjacent to the brace, with plenty of air movement, you probably wouldn't have a problem. James (Salty Dog)>

Hey, It's Gettin' HOT in Here! Lighting/Metal Halide To the crew, Hello and thank you for taking the time to answer my questions. First I would like to know if, in your opinion, two 175 watt metal halides would be adequate to light a lagoonal-type SPS dominated 46 gallon bowfront aquarium? The lights are just about 8 inches above the water surface. This leads me to my second question, with the lights being so close and the tank located in an alcove, the water temperature reaches 83 degrees, what is too high for SPS corals? I realize that there is no one set temperature but I am concerned that when the corals are eventually added this temperature will be a problem. Lastly, as I do not have a chiller and will not be able to purchase one immediately, I have an idea to use a dryer vent system and vent the excess heat away from the tank, do you feel this would help to control the temperature a bit. Thank you again.  <Yes, it would as long as the vent system is powered by a fan, I believe that is what you meant. James (Salty Dog)> 

Hey, It's Gettin' HOT in Here! Lighting/Metal Halide Follow-up James, Thank you for the quick reply. To clarify my idea I will use the fan on the halide hood to move the heat from the bulbs through aluminum vent material into another room. Do you think this is a workable plan? It's better if you can pull the air through the vent rather than push it. Sounds workable to me.> I would also like your opinion on the use of two 175 watt metal halide bulbs on a 46 gallon bowfront, the dimensions of which are 36 inches long with a depth of 18 inches. I would like to stock the tank with lagoonal-type SPS in the upper half of the tank and slightly lower light SPS below. The bulbs are about 9 inches from the water surface. I will be using two XM 10K bulbs with actinic supplementation. Assuming proper water chemistry, will these two bulbs be able to provide the proper light for the corals?  <Most definitely. Matt, next time you reply, do it on the original message as we get plenty of mail and when we get a return such as yours, it's hard to remember what was originally said. It helps to be able to reference the original query. Thanks. James (Salty Dog)> Thanks again, Matt  <You're welcome>

Metal Halides over Acrylic Good Afternoon/Morning crew at Wetwebmedia, <Good morrow to you> I have a question on Metal Halide lighting and I was wondering if I can pick your brains one more time. :) I currently have a 157 gallon acrylic tank( height is 29 inches and 18 inches wide). It's been up and running with 3 VHO bulbs (420 watt) for 2 1/2 years now and houses mostly soft corals (leathers, polyps, pagoda cups, Xenias etc..25 total) I've been thinking of upgrading my lights to metal Halides so I can put in some clams + SPS corals. However, I am concerned that since my canopy is for standard fluorescent lights - approx. 7-8 inches tall (not the super tall canopy for halides), if I could get a way by keeping the 2 VHO lights and by installing 1 or possibly 2 150 Watt low profile Ocean Light HQI halides (saw some at Dr.FosterSmith)? <You are wise to be concerned here... MH's are hot, the flashpoint for acrylic low> My main concern is whether the halides (1 or 2) would affect the acrylic. There are 2 struts with 3 openings. If I placed the halides directly over the openings, not above the struts, would I be able to install them and enjoy some relative peace of mind (assuming they won't crack the acrylic or cause it to craze)? <Maybe> The Ocean Light HQI halides are 2 1/2 inches tall so they'd be roughly at the same height my VHOs are currently at (approx. 8-10 inches from the surface water.) What should be the minimum distance from the acrylic for 1 or 2 150 watt halides? <I'd consult with the manufacturer re this> I am planning to have a fan blowing either across or at the water to control rising temps. <Will help> Any ideas if this scenario is safe? Are halides safe over acrylic as long as they're not placed directly above the strut braces? Your input is as always invaluable... <I give you good odds of not having trouble here... considering the distance, over water, the wattage, use of fans... Bob Fenner> Thank you very much in advance... Dimitris

Lighting Quandary...Part II Okay, one follow up question then.  I have a canopy on my 55 gallon tank and my wife and I both really like the way this looks.  If I were to go to a pendant system, can I mount them in a canopy? <If there is enough clearance and sufficient ventilation and fan cooling, you can definitely do this. I have pendants mounted in the canopy over my reef system.> Will I need to worry about temp under my canopy and possible overheating.  (I may already have a problem since my current temp.s in the summer for Freshwater run in the low 80s for about 3 months.  I'm looking into fans to see if that will cool the water enough to get it back down to about 79 degrees.).  What do you think? <Well, cooling and ventilation are huge issues when mounting pendants in the canopy. My canopy was designed specifically for pendants; you may need to see if yours will work. You should allow at least 6-8 inches of clearance above the water, and a little more room for ventilation.> Thanks again for your input and support of all of us that are trying our best to learn what we need to keep these beautiful and fragile creatures in our homes and under the best possible conditions! Jeff Smith <Glad to be of service, Jeff! Good luck! Regards, Scott F.>

Fluorescent to MH blues... too much heat, vacillation in temperature in a SW 55 Hello all, I just purchased a new light for my 55 gallon reef tank. I went from a compact fluorescent which was about 130watts total to a metal halide system. I wanted to be able to get some of the cool corals. I already have a few corals and they seemed to be doing alright with the other light but figured they would love the new light. The new light is a Current USA Outer Orbit fixture 48'. It has 1x150W 10K HQI-MH 1/ 2x130W Dual Actinic & 6 Lunar Lights. I Have it mounted almost 13' over the tank. The problem that I'm having is that the temperature in my tank has sky rocketed. It's usually 76-78 and since I have added the light it's gone up to 86 which I know is on the high end. The fish and the corals seem to be doing alright but I don't know what the long term effect will be. I keep the AC in the house set at 70 and I still can't get the temperature down below 81. When the light comes on the temperature climbs to 86 before the light goes out. Is the light too much for a 55 gallon tank? <As it is, yes... you have too much thermal fluctuation for health and safety's sakes> I've looked into chillers and they're so expensive. The light cost a fortune. Is there anything that I can do to get the temperature down? <A few things... evaporative cooling by supplying fan/s to blow air across the surface would help... elevating the light even more over the tank... adding more volume... in a BIG sump/refugium elsewhere, that's tied in with the 55...> What's the long term effect? <Shortened life-spans for your livestock, big electrical bills... all that goes along with these> Set up is a 55 gallon tank set up in December 2004. Filtration - Eheim Professional II Canister filter up to 92 gallons. Protein Skimmer - Aqua C Remora with Mag Drive Power heads - 2-600, 1 1200 Maxi Jet, 1 Zoo Med Power sweep 228 Heating System - Hydor Eth 300 External Thermal heater 75 pounds of Fiji Live Rock, 60 LBS of Fiji Pink Aragonite Live Sand. Kent Marine Maxxima 35 Hi-S R/O / Deionizer 4 Stage Reverse Osmosis Unit. Current USA Outer Orbit Fixture -- 48' 1x150W 10K HQI-MH 1/ 2x130W Dual Actinic & 6 Lunar Lights Inhabitants -- 1. Purple Tang 1. Blue Damsel 1. True & 1 False Percula 1. Lawnmower Blenny 1. Dottyback Fridmani 1. Diamond Goby 1. Branch Coral - Paralemnalia or Lemnalia Tree Corals, Finger Leather, Branch, or Cauliflower Corals 1. Red Feather Star 1. Torch Coral -- (Brown) Large Polyp Stony 1. Red Star Fish Misc. Hermit Crabs Misc. Snails <Bob Fenner>

Adding MH Lighting 2/5/04  Hello again! You guts are great. Thanks for the help in the past.  <Hi Jim. Glad you have benefited.>  I have a 120 gallon tank that is 4'x2'x2'. I currently have 700Watts between PC and VHO. I want to get rid of the PC and change to a 250Watt 10K MH (I already have the MH). The problem/concern that I have is that I currently have my lighting under a hood. If the MH fixture can fit under the hood, will it be okay to run with two 4'' fans for cooling?  <It should be, but it is hard to guess. Depending on where you live, whether you run A/C in the summer, use a chiller, photoperiod, etc., the fans may or may not be enough to control heat.>  Will there be an issue with placing the fixture on top of the glass cover?  <If you meant the glass aquarium cover, yes. The heat from the lamp may dangerously overheat the glass cover if it is too close. Also, most reef keepers don't run glass tank covers because of the amount of light the block, even when clean.>  Another idea that I had was to remove the bulb from the fixture and mount it to the top of the hood with a piece of sheet metal to deflect the heat from the hood and still using the reflector. I would still use the fans to cool the light, but I am not sure if this is a good idea. Any other suggestions to improve lighting and still keep everything under the hood?  <If your MH is contained in a pre-made fixture, I would try to use the fixture as is. It should be at least a few inches from the water surface to protect it from serious splashing. I would consider cutting a hole (or other wise re-engineering the hood) and recessing the fixture in the top of the hood before I would dismantle the pre-made fixtures. Best Regards. Adam> Jim Martz Sr. 

Lighting and supplementary equipment questions 2/26/04 Dear Mr. Fenner,  I am 11 years old and have a 60 gallon reef tank. <Hi Evan.  Adam here today.  Congratulations on such an early start to the hobby!  So many years you have to enjoy it!> I check my water parameters each day and perform water changes 10% every month. I was thinking about adding to my lighting system of two 96 watt power compact bulbs. I was thinking of adding two 150 watt 20,000k metal halides. If I did this would I need  a chiller or could I use three of four cooling fans? <If your house is air conditioned in the summer, you may not need a chiller.  A couple of fans will often work fine.  You will need to consider the noise, appearance and added evaporation in your decision.  If you want to keep animals that you really think need halides, you may want to consider the compromise of a single MH over the center.  That way you will have areas on the sides for lower light animals.> I was also thinking about adding a calcium reactor and a nitrate reductor to my tank. Would these be necessary? Would i need a sump for these? Could they sit under my tank using plastic tubing to get and return the water to my tank? Could you please e-mail me back. Thank you in advance.  Evan Morris Santa Monica, CA <You can run these devices without a sump, but you might need pumps to move the water through them.  A calcium reactor is nice for the convenience of not having to make daily Ca and Alkalinity additions, but is not necessary.  A nitrate reducer should be totally unnecessary for a properly set up and maintained reef tank.  If your nitrates are over 10 or so, you should correct the source, not just try and eliminate the nitrate.> P.S.  I loved the Conscientious Marine Aquarist. It was a huge help for me when I started reef keeping. I have read every page at least 3 times each. <Bob sees all of these messages, even when he doesn't reply personally, and they are all very much appreciated.  Best Regards, Adam><<Ah, yes. RMF>>

Mounting MH pendants in a canopy Dear crew, <Matt> First let me say thanks for all of the valuable information you provide on your site. Now on to the question. I recently purchased a pair of PFO DE HQI, 250 watt mini pendants. I want to mount them into a hood. Can I just mount the metal pendant case to the top of my canopy or do I need to leave some room between the pendant and the top of my canopy for air circulation? <At least you should make sure there is sufficient thermal insulation between the fixture and (especially flammable) canopy structure... this may be just a piece of aluminum... The air circulation question can be addressed later, with measure of your water temperature... some folks get away with simply drilling a hole on either end of their canopy, possibly one or more through the top... others find they have or want to add a fan or two to push air in/out> I have sent the same question to PFO unfortunately they have not responded to my request for information. Any suggestions would be greatly appreciated. Regards, Matt <Be chatting, Bob Fenner>

Aquarium cross braces I appreciate all your support in the past and am presently trying to solve a problem with my 330g tank. It is 84"x30"x30" and it is 3/4" glass. When the built the tank in my home they put two 1/2" glass 14" cross braces in 14" from each corner. This lead to a 14" opening 28" opening and then a 14" opening. The problem I am having now is the left and right halide is directly over the cross brace. This is dimming the light and I am sure must be changing the spectrum of the bulb. <Agreed> Not to mention also warming the brace itself. My question to you is do you know, or know someone that would be able to help me fix this with problem with smaller braces having to be thicker or some other solution? <Not smaller... but you could cut the current braces and move them to the middle of the tank> I know from what I have read that they should have spaced them out more evenly. This would have helped to some degree but the braces need to be about 8" wide to really help with the lighting. Thanks a lot for your help and have a great day, Ian. <Is it worth considering moving the lights out over the side cut-outs and adding a third (perhaps higher wattage and temperature) MH to the middle area? Bob Fenner>

Re: Aquarium cross braces I am sorry for not giving you the complete information on my lighting. Currently I have 3 175W Halides 10000K and two NO Actinics. I also have a combination of SPS and LPS corals, clam, leathers.  I don't mind your idea of moving the lights around. I could move the two end ones out over the 14" opening. Then I thought I could add another 175W Halide to the middle opening so there would be two. Would this be enough lighting for over my tank or should I consider getting two more halides of higher wattage for over the cross braces. <For this depth (30 total inches if memory serves) I might well increase the wattage of the center MH... perhaps a 250 Watt Pendant... and move your clam, perhaps some SPS there> If so what would you recommend for over my 30" deep tank? Thanks for all your help it is greatly appreciated. <Many possibilities... perhaps review the MH FAQs archived on WWM re others choices in lamps, fixtures. Bob Fenner>

-Mounting fans in canopy- Dear Crew I just received my MH/PC retrofit. I also bought 2 Ice Cap fans.  My question is this: What is the best way to place them?  One at each end of the fixture? Across from each other?  What? <One on each of the long ends, one blowing in, one blowing out. Good luck with your new lights, and enjoy the new found heat! -Kevin> Marion

Tank lighting too hot - 12/15/03 Hola crew,     I have spent hours upon hours on your website, researching fish, clams, and many other Marine aquarium things. <Know what you mean and now I work here......oh =) Let us know when your ready to take the challenge, eh?>  I recently upgraded from a 55 gallon to a 140 gallon tank.  I just got the 400W MH lights hooked up, and my temperature soared! <Yikes> Its semi cold where I live (Fresno, CA.) and the temp can vary. <To say the least>  But the house is usually 65-70 (in the winter)  Summers here get into the 100's. <millions>  Anyway, I had the temperature at 78.3, and today I installed my new lights and in two/three hours the temp went all the way up to 82.5, and I finally just shut the lights off. <Good idea.>  I have read the chillerfaqs and am going to try a couple fans tomorrow, but not sure if this will bring the temp down, considering I am not even sure if it was done going up. <Likely not. I had a similar problem with my 250 watt MH added to my 20 gallon. I am using a dual Aqualogic controller with the heater plugged in one receptacle and a fan in the other (blowing over he water and light). Once the temp gets to a certain programmed temperature (programmed by me) the fan kicks on and once it cools the water to a certain point the controller kicks the heater on.> I would have let it go up until it got to a stable temp just so I know, but unfortunately in my excitement I transferred some of my coral over before I tested the lights! <Whoa>  Brain fart. <Happens. Know what you mean> And the lights are only about 6-8 inches from the water. <About right> Do you think fans would work for me? <Fans could easily help> Or do I need to get a chiller? <In Fresno it is not a bad idea.>  I know nothing about chillers so any advice here would be great. <Not too big of a deal but pays to read reviews and recommendations. Look at cost not only in device but also in upkeep and electrical cost to run>    Thanks! <You bet! Happy Holidays ~Paul> Phil

Acrylic Tanks and MH Lighting We are in the investigating process of the "big tank" (650 gal). We want to leave the top open and use metal halide pendants for lighting since everything except the viewing window will be behind the wall. In one of the quotes for a custom tank the dealer said the tank has to be glass because the metal halides will destroy an acrylic tank. I have never heard this before and we had really decided that acrylic was the way we wanted to go. Is there any truth to this? Thanks in advance for your help and for the MANY questions that will be coming your way in the next few months. Beckie <No truth to it as far as I'm aware... Our old companies installed hundreds of acrylic tanks with metal halide lights in them... Bob Fenner>

Acrylic Tanks & MH Saw the post about MH and acrylic tanks. Just wanted to add that most acrylic tanks leave a considerable amount of acrylic in the top pane for structural support. A MH placed directly over one of these acrylic struts will likely cause that to crack. <Ahh, yes... Needs to be offset, and even then, suspended per manufacturer's recommendation... per wattage, a good distance above the top> But as long as the bulb is over a cut-out it should be fine. (I'm speaking from personal experience: I cracked one of my struts with a misplaced MH bulb. Others have traded thin acrylic panes on standoffs as heat shields; not sure if this works.) <Me neither. Likely not absolutely> A professional acrylic aquarium craftsman also warned me that the normal practice of polishing the top pane in order to round the edges of the cutouts can result in "crazing": a network of fine surface cracks that can, over time, develop into a real problem. MH bulbs might make any potential crazing worse. He bevels his edges rather than polishes them to reduce the risk of crazing. Marc <Good input. Thank you, Bob Fenner>

Re: halide/glass cover Can halides be used over a tank that is covered in glass tops? If no for corals/photosynthetic orgs. , how about in a FO ? Would the rippling effect still be apparent with the glass? <Yes and yes. However, air circulation will be needed to disperse heat and provide proper air exchange.  Best to use eggcrate cover, not a solid top.  Most MH users use several fans....the danger is overheating.  Craig>

HQI lighting I've been reading a lot about HQI lighting and would like to have your opinion on them. Are they lights that would need a lot of equipment to cool the tank? <Aka metal halides... do produce prodigious amounts of useful photonic energy... but as you state with concurrent high energy use, heat production. Please read over the many sections on light, lighting and associated FAQs posted on our site: www.WetWebMedia.com in many sections... starting here for Marine: http://WetWebMedia.Com/lighting1MAR.htm Bob Fenner>

Cooling Fans Hi Bob, I have a mechanical question for you. I am embarking on adding MHs to my hood, and I know the heat will rise considerably. I plan on adding (for starters) one fan to the hood. If need be, I will add a second. <Good idea... one in/out> I was going to ask what I thought would be a stupid question: Should the fan pull room temp air into the hood, or should it force hot air out of the hood? I searched all of the FAQs on the site, and I found where you recommended two fans in hoods -- one pulling in, and one pushing out. So . . . I guess it's not a stupid question. With that, what should I set my initial fan to do -- pull in or push out? <Out my friend> If I get to the point that I need a second fan, are you still of the mindset of having one pull in and the other push out? <Yes> Many thanks! Dale. <Bob Fenner>

Halide Lighting Distance Hello, Just wondering about the basis for the suggested minimum distance from the water surface for MH lighting. <Six inches is as close as I would get.> I have just bought a nice AB dual setup but find the spread of the fitting means a lot of spill from the edges unless it is quite close to the tank surface. While the recommendation varies from 20 inches to 10 inches (min.), can you tell me if this is because of potential heat loading or UV emission or something else? <The closer you get the greater the risk of substantial heat transfer and water splashing and shattering the lamp. Also, when you lower the lamp you increase the light intensity, so you must do this slowly. The UV should be taken care of by the shield, either built into the lamp or fixture.> Best regards, Jordon Peters <Have a nice day. -Steven Pro>

MH lights: mounting distance Hi! Bob, <Anthony Calfo in your service> I have a question about mounting metal halide lights on top of aquariums. I have a 250W and 400W on top of a 240 gal acrylic tank.  <I assume that you have a tank full of SPS coral else you have way too much light. Of course, you may instead be trying to make lava...Hmmmm?> The halides are only 4" above the tank which is covered by glass.  <OK... making lava it is...> Yesterday the glass broke and the top of a acrylic has a major crack in it. I assume the region is getting too hot. <that would be correct, and an understatement my friend> Questions: How far above the water level do you recommend for the halides? <9-16" depending on the invertebrates needs and lamp intensity. You will likely want to be 12-16" off the surface of the water> Does the tank need to be covered and if not will the water evaporate and cause scaling on the bulb? The tank should have some kind of guard at least to prevent jumping fish. This could simply be a plastic light diffuser for drop ceilings (AKA egg crate). And the lamps separately may/will need some sort of UV lens. The topic is debatable regarding it's impact on coral pigmentation. But the closer you are to the water, the more you will need that lens for several reasons... not the least of which is the hot bulb shattering if cool water should be splashed upon it. Do check out the following link for further reading: http://www.reefs.org/library/talklog/s_tyree_060202.html > Thank you. <best regards, Anthony Calfo>

Metal Halides Too Close to an Acrylic Tank? Hi guys, I have to tell you that WetWebMedia.Com has been an excellent source of information so far. <Thank you. Be sure to tell your friends.> I think I may have been taken in by the guy at my local pet store, though. I'm moving up from a 65 gallon to a 180 acrylic, rough measurements 70L X 24H X 18W. The oak canopy he sold me is only 6" high, though. I'm concerned that mounting 3 metal halides under this canopy will put them entirely too close to the acrylic tank top. There will only be about 1 1/2 - 2 inches of clearance from the metal halide bulb to the surface of the acrylic. Isn't that too close? I'm concerned about possible damage to the acrylic itself. <Damage to the acrylic and to the animals is a very real possibility. MH's lamps are generally mounted 6" to 12" away from the top.> Also, I intend to place a lot of hard corals in this tank. Would you recommend 3 250W MH's, or 3 175W MH's? <If hardcore SPS, go with the 250's. If more of a mix with LPS and some soft corals, the 175's will do fine. SPS will grow well also under the 175's. Invest in quality lamps. Aqualine-Buschke and Ushio are excellent in 175 wattages. Those two along with Iwasaki's in 250 watts.> How about 2x6500K and 1x10000K? <For the 250's, I would use 3-6,500K Iwasaki's with supplemental actinic. For 175 watts, I would use the 3 10,000K Aqualine-Buschke's with or without extra actinic.> I will be using supplemental PC Actinic lighting, also, probably 2x96W. Since I am still early in the planning stages, any help/ideas at this point is GREATLY appreciated. Thanks for any advice you can give me, Will <Do read through the files and FAQ's for lighting for additional information. -Steven Pro>

HQI lighting Hello, I currently have a 120 gal reef (48 x 24 x24) with a variety of SPS, soft corals. Due to my 430 dollar a month electric bill (Thanks Gov. Davis!!) <$430...whew! Consider a cheaper hobby... like drug abuse> I recently removed the two 250 watt MH bulbs from the tank and replaced it with a 4 x 96 watt Power compact hood ( 2 actinic and 2 10,000 k bulb) and also have 2 110 watt VHO Actinics. .  <Hmmm... perhaps not a great savings all things considered. 400 watts of MH light compared to 400 watts of PC light are not the same. MH is far more intense=more bang for your buck. Your corals are getting MUCH less light (easy to confirm with a Luxmeter at the surface and even more so at 12" water depth> I also have a 300 gal marine fish only tank and had an outside 60 gal grow out coral tank which had the power compact set up I just mentioned. Anyways, by getting rid of the 500 watts of MH from the 120 in addition to breaking down the outside 60 gal, I lowered our electric bill by over 200 bucks!!  <excellent... but has less to do with the lights... perhaps as much or more with pumps/heaters removed> The corals in my 120 include: star polyps, colt, pink Button Coral, mushrooms, green finger, hammer coral, Fox coral and green pin leather. Anyways.... Some of the green corals (star polyps, green finger) have turned a little brown since I took of the metal halides. I have been told that I may have too much light which is why some of the corals are turning brown?  <yep... predictable. Lower light has stimulated the zooxanthellae (brown dinoflagellates) to increase their resident populations in symbiosis. a common and perhaps harmless change> I think that under the metal halide the green corals looked their best (had 500 watts MH, 220 watts VHO actinic and also 80 watts of regular flourescent)800 watts total now down to the 384 (pcs) and 220 VHO which is just over 600 watts. Now for the question. I would like to go back to metal halide supplemented by VHOs but want to go with a much lower wattage, like two 150 watt HQI dbl ended bulbs? <the double ended bulbs have got some great reviews> I am researching the HQI ballast/bulbs because it seems to be kind of new still and now a lot of info is known. I am still looking for the article by Sanjay Yoshi but have not found it yet.  <a keyword search of Sanjay's name on the Google search engine for WWM and abroad comes up with many hits for his work all over the net. Please explore the first link for his general homepage and the second link for one of his very good studies/articles. More o be had if you will explore: http://www.personal.psu.edu/faculty/s/b/sbj4/aquarium/aquarium.html http://www.personal.psu.edu/faculty/s/b/sbj4/aquarium/ballast%20comparison/ballast-comparison.html> Anyways.....is there a difference between a dbl ended bulb versus a screw type? I saw a 150w HQI ballast (made in Taiwan) it takes a screw type bulb. I have read and heard that the dbl ended bulbs burn brighter?  <they do have a great early reviews> I would just have to worry about the U.V lens? <usually necessary> I am considering going with the 300 watts of HQI metal halide supplemented by the 220 watts of VHO actinic and maybe additional 80 watts of actinic. I realize if I put back the 80 watts of actinic plus the 220 watts of VHO actinic I am back to 600 watts of light,  <hmmm... so many lighting choices, but I am content with tried and true solutions. All of the better rated "regular" MH lamps have been shown to have enough blue/actinic light and require NO supplementation. If you want a simple solution, choose 2 or 3 6500K Iwasaki 150 watts (or 2 250 watt lamps) or the same number of 10K Ushio or Aqualines if you like a bluer colored daylight. Extra fluorescent lighting will only be for aesthetics if you like> If I don't I am cutting back about 80 watts. But would the intensity from two 150 watt HQIs put out more lumens than the 4 x 96 PCs?? <yes... MH type bulbs in general are far more intense... better deals> I will be searching for some HQI ballasts (Champion Lighting, Hamilton etc....) to compare to the Taiwanese made one I saw at my local fish place. If you have any opinions about the HQI ballast/bulbs versus the electronic Ice Caps MH ballasts or standard coil/tar ballasts could you please share your opinions with me. <fine with cap and coils.. I am strongly against electronic metal halides based on published and yet unpublished reports I have seen. Misleading and inaccurate marketing of these products> Again, I am very concerned with my electric bill so I am thinking that by using 300 watts of HQI instead of the 384 watts of PCs may help and also make the tank look a little brighter and some of the green corals get their intense greens back? <correct> Thanks for your time. Kerry Kanno <best regards, Anthony>

175W v 250W halides Have enjoyed reading all FAQ's but still looking for the definitive answer to my question. I am doing a custom 68X24X24 installation in my home and have been debating whether or not to go with three 175W or three 250W MH bulbs with or without VHO Actinics.  <rest assured.. an easy question> I am new to reef aquariums, but my goal is to reproduce a shallow Indo-Pacific reef with lots of SPS corals. I'm sure that I will start with less finicky species but I want a system that maximizes flexibility and will have plenty of capacity for more demanding species later.  <even still... you probably do not need the 250 watt bulbs. The tank is shallow enough and the beginnings with less demanding species may be very difficult with 250 unless the tank is hardcore SPS and clams (few or no Corallimorphs, zoanthids, LPS and the like)> The tank will be placed in a wall niche and there is a 3' space overhead that can be used as sort of a very tall hood.  Halide placement will be 9-18" above water. <Around 12-16" is typical> Therefore, I can regulate light to a degree by raising and lowering individual pendants. <not recommended unless you will use a Luxmeter concurrently. Else it is dangerous guesswork with symbiotic animals.> I would also like to maximize the height of the lights to reduce heat transfer and make access a bit safer.  <the heat from a well made pendant or hood is no different for VHO than MH... they all produce heat and can be tempered by an inexpensive to buy and inexpensive to run muffin fan (8-12 watt). Really a better solution than tempering the efficacy of high dollar and useful lamps> However, I don't want to go overboard and generate extra heat and consume watts that I don't have to. <the heat issue is an overblown marketing artifact of people that sell fluorescents... you can easily get burned on VHOs just the same and MH lamps categorically give one more bang for the buck (value) than any other lighting... especially for SPS corals> Is there a good source for information on light distribution patterns for various MH reflectors? Most of the specs I have seen say that they will light a 2'X2' area but they don't say at what height. <Sanjay Joshi has done a lot of great work on this topic. Link to his work on our links page or do a keyword search of his name. Great stuff> How can one make a reasonable estimate of light loss with depth through water assuming average transmission properties (if there is such a thing) for a well kept, low organics reef aquarium. <Luxmeter is a very useful tool to illuminate the efficacy of MH over fluorescent. Also, add VHOs only for any aesthetic preference that you might have. They are not needed otherwise. Good metal halide lamps have enough blue spectrum. Go for Iwasaki 6500K, Aqualine or Ushio 10K> Best regards, George Nikolich <with kind regards, Anthony>

Re: 175W v 250W Thanks for the advice, very helpful. Think I'll go with the 175's. <<Greetings, hopefully I can continue the helpfulness trend...>> This aquarium will be dead center in the middle of my house with no easy access to exterior walls, nor do I have access to the attic. Therefore, I am concerned about proper ventilation and the need for a chiller. We are looking at possible temps tomorrow of around 110°F (unusual, but not by much for July & August in Fresno, CA) that means I may see 80°F indoors. As this is already at the limit for aquarium temp, I assume that there is no way that I can add any heat from lights or anything else without running a chiller. <<is a go assumption, yes.>> I had planned on putting all the hardware, including ballasts, in a closet that shares a wall with the aquarium niche. I don't think that there will be a problem with heat from pumps, etc., but how about if I add a chiller? <<That would definitely be a problem.>> Does a chiller of appropriate size for this system generate too much heat to be confined in a 4'X6'X7' space without active ventilation? <<Oh for certain...>> If I exhaust the air from the hood and the closet into the interior of the house, will I be sorry and wished that I found a way to exhaust it outside instead? <<I would think so, yes.>> I can run a duct to an exterior wall but it would not be a small project. If I do run a duct outside and install an exhaust fan ((150CFM split between hood and closet), would there be any need for muffin fans? <<They certainly wouldn't hurt.>> I know its hard to be specific when you don't know the exact layout, but I am just trying to get an overall feel for how much heat is generated by a complete system and whether or not the interior of my house can handle it (2,000ft2 downstairs where aquarium will be and 1,000ft2 upstairs, lots of ceiling fans). Regards, George Nikolich <<Cheers, J -- >>

Acrylic Tanks and MH Lighting We are in the investigating process of the "big tank" (650 gal). We want to leave the top open and use metal halide pendants for lighting since everything except the viewing window will be behind the wall. In one of the quotes for a custom tank the dealer said the tank has to be glass because the metal halides will destroy an acrylic tank. I have never heard this before and we had really decided that acrylic was the way we wanted to go. Is there any truth to this? Thanks in advance for your help and for the MANY questions that will be coming your way in the next few months. Beckie <No truth to it as far as I'm aware... Our old companies installed hundreds of acrylic tanks with metal halide lights in them... Bob Fenner>

Acrylic Tanks & MH Saw the post below about MH and acrylic tanks. Just wanted to add that most acrylic tanks leave a considerable amount of acrylic in the top pane for structural support. A MH placed directly over one of these acrylic struts will likely cause that to crack. <Ahh, yes... Needs to be offset, and even then, suspended per manufacturer's recommendation... per wattage, a good distance above the top> But as long as the bulb is over a cut-out it should be fine. (I'm speaking from personal experience: I cracked one of my struts with a misplaced MH bulb. Others have traded thin acrylic panes on standoffs as heat shields; not sure if this works.) <Me neither. Likely not absolutely> A professional acrylic aquarium craftsman also warned me that the normal practice of polishing the top pane in order to round the edges of the cutouts can result in "crazing": a network of fine surface cracks that can, over time, develop into a real problem. MH bulbs might make any potential crazing worse. He bevels his edges rather than polishes them to reduce the risk of crazing. <Good input. Thank you, Bob Fenner> Marc

Reef Lighting  Aloha, <Greetings.> I have a 75 Gallon tank. I am not wanting to take a shortcut on lighting. I want to keep some SPS and clams. I keep my house cool (about 70 degrees) I will have 4 - 4" fans in my custom enclosed canopy over the tank (hanging pendant- style out of the question unfortunately). My canopy will be about 8 to 12 inches over the tank. I plan to purchase a sheet of polished aluminum and line the entire inside with it. <I'd get it at least coated with something... aluminum and saltwater don't mix well.> On to the lighting... I would like to retrofit 2 - 175watt 10,000K metal halides.  Complementing that, I can either buy an Icecap 430 and run 2 110watt actinics, OR I can purchase a 660 and run 2 110watt actinics PLUS 2 110watt 10,000K bulbs along with the halides. Is this overkill? <Hard to discern... you probably don't 'need' the extra 10K fluorescents.> Again, I would like a T. maxima or T. crocea in the near future. But I don't want to burn the SPS corals. <Make shady areas with the rock work OR drop one of the metal halides and light with the other on one side of the tank only, and then perhaps use the 10K VHOs on the side that doesn't have the MH lighting.> OK, if you're still with me, back to the MH. I have heard about UV rays, so I assume I will have to build some sort of UV lens for my MH. <That is correct.> Is this a special type of material or could I use a piece of acrylic? <I would use glass - acrylic will likely melt being that close to a lamp. Glass is available with a UV-filtering coating.> I could build a " box" over each bulb with it. Not sure if the bulb would melt it though. <It would.> I really don't want a piece of glass or acrylic over my entire water surface. I want evaporation for Kalk top-offs and cooling factor (with the fans blowing across the top of the water). <You might need to rethink this, with fans sucking hot air out of the canopy.> I am trying to come up with a plan to where I do not have to use a chiller, but get sufficient lighting. <I'd skip the canopy and instead light from above with adequate space for more fans. You will soon see that the canopy becomes a trap for heat, and you largest problem will be getting the heat out of the collector.> I have so many ideas in my head so if you could blindfold me, spin me around 15 times and point me in the right direction, that would be super cool groovyrific!! <Again... if SPS is part of your goals, then skip the second MH. Light that side with only fluorescents. You will still have issues with heat... you may need more fans or you may even need a chiller. Time will tell.>  Mahalo, Jason <Cheers, J -- >

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