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FAQs about Light and Lighting for Marine Systems, Waste Heat Matters

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The life in your system can't "go elsewhere" even if it were able, if the temp. gets out of whack.

Temperature Control/Cooling Marine Tanks 5/22/11
Adam J.,
<<Hello again Edward, sorry for the day late response, I didn't notice your message in my box and I was out of town last night.>>
I am sorry to keep bothering you.
<<No bother at all.>>
I had a bit of a problem with the temperature of my tank today. Today we had weather in the mid 80's ( I live in Michigan) and my temp went from it's normal 78.5 degrees to 81.5 degrees.
<<81 degrees isn't unheard of on the reefs, actually it's still in the acceptable range for a lot of denizens, what you don't want is the swing from 77-82 everyday.>>
I believe the raise is do in part to my 2x250 watt MH light fixture.
<<Definitely a huge source of heat, I live in Southern California so this was something I had to plan for in the summers as well.>>
When my lights aren't on my temp is VERY solid at 78.5 due to my reek keeper lite. They are on for 11 hours (7am-6pm) and the temp climbs to 81.5 right before the lights go off then within 5 hours of lights out it fully decreased to 78.5. I have 2 cooling fans on my wood canopy one is a modified high quality fan that blows air in on one side.
The other is a somewhat large computer type of fan that sucks air out. They are also controlled to go on at 78.8 and off at 78.7. My temp has not peaked past 79.5 degrees before today. So I know the warmer air plays a part in this too. My question is should I not fight this and raise my temp to 80 or would it still climb and get up to say 83? I will be adding another fan near my sump but I don't think that can lower it 3 degrees by itself.
<<Raising it to 80 would negate the swing back down to 77/78 at night but would still expose you tot he risk of it climbing out of the acceptable range during the day...there is no ceiling in place so to speak. Adding an extra fan above the tank or even in the sump area would definitely help out, though you can/may have extra evaporation so keep that in mind/check. I forget if you're running a lighted refugium in your sump but having this light on a reverse lighting cycle could also help would heat stabilization as their would not be two sources of heat via lighting on the same time of your system everyday.>>
Also a chiller would be a financial back breaker right now.
<<Understandable, they have their own issues/maintenance as well, though in some cases can end up being a necessity, hopefully for you this doesn't turn out to be the case>>
Any insight is most appreciated!
<<Check these out if you haven't;
http://www.wetwebmedia.com/chillersmar.htm >>
Thanks again and again and again,
<<No problem!>>
<<Adam Jackson.>>

Lighting System Causing Temperature Problems (Red Sea Max 130d) -- 05/21/10
<<Greetings James>>
Thanks in advance for your guidance.
<<Welcome, in advance>>
I am currently cycling my first tank. It is a Red Sea Max 130d.
<<Neat looking little systems>>
It is a 34 gallon tank. I am having problems with temperature fluctuations caused by the lighting. This system uses 2 55watt T-5 compact bulbs. I started with a 10 hour on 14 hour off light cycle.
<<This is fine'¦what I would do>>
This caused a temperature rise from 77F to 80.5F.
<<Mmm'¦not 'all that bad' considering'¦in my opinion>>
I then attempted to use the supplied optional cooling fan but the water still rose to 80F.
<<But still, a 0.5 degree drop'¦this is of benefit>>
I tried breaking the light cycle into half, 5 hours on 5 hours off 5 hours on 5 hours off.
<<Depending on your livestock this 'may' be fine'¦but just too 'unnatural' for my liking>>
I am now seeing a temperature fluctuation of only 1-1 ½ degrees Fahrenheit. I am in no way able to afford a chiller right now so I don't know what else to do. I eventually plan on getting some soft corals so I was wondering if a split light cycle would be harmful to fish or inverts.
<<Considering the lighting system, I would suggest the longer (10 hr) 'on' cycle to allow the corals to 'maximize' the available light output. The temperature swing and max-temp you describe is workable in my experience. Do utilize the cooling fan'¦and try leaving the front opening 'up' to facilitate air movement and some evaporative cooling>>
James (North Carolina)
<<Happy to share'¦ EricR (South Carolina)>>

Re: Watt per Watt heat generated 5/25/09
Hi Scott,
<Hello Ranjith.>
Ok now let's swap the NO tubes with 6 bulbs PC of 36watt each and 2 actinic NO tubes 20 watts each.
And to get a real scenario let's consider the aquarium as well :)
The PC would have to be mounted 3-4 inches above water level in a closed wooden hood.  The 150 watt MH would be 6-8 inches above water level in an open hood (10" tall hood will look silly on a 24" tall tank)  This given, would the MH or PC heat the water more?
<On just my judgment call here, I would say it is about even.>
This will result in the chiller running more and heating the room even more.  The uncrossable bottom line, is I cannot afford to put an AC to cool the room.  Do let me know what you think will work.
<Well, if you need that many PCs for what you keep I would just go with the MH.  Cooling fans over the water will keep the tank temps down somewhat, keeping the chiller from running more than necessary. The bottom line is you may need to ventilate the room too depending on the ambient temperature. Do realize this is not that much lighting, but if it crosses that line it does. Both of these setups are going to impart close to the same net heat into the room IMO.>
<Welcome, Scott V.>

Re: Watt per Watt heat generated 5/25/09
Hi again Scott
To get this closed, sorry but a little off track question.
<No problem.>
The tank is 36"x24"x24" - 90gal.
Substrate will be 1" sugar fine aragonite.
Considering the overflow is at 1.5" below the rim, the Water column will be 21" high.
I plan to keep softies and LPS(2-3).
No SPS or Clams.
Predominantly leathers actually.
How many 36watt 6500k power compacts would you suggest?
<Four or so, actually I would run dual 96 watters here.>
Would 6 that I plan not be needed assuming I line the closed hood with reflective material and use two 4" fans pulling air out the top?
<Nah, I think 4 will do fine.>
Sorry for the deviation from the core subject again.
<Welcome, Scott V.>

Re: Lighting.... again. Lighting.... again/chilling? MH waste heat... 9/8/08 Thank you so much! <Happy to help.> Just to clarify... do you think I would need a chiller for the twin 175w Halides, or just with the twin 250's? <I can't really say for sure, there are so many factors that contribute to this, but it is likely possible you will need a chiller with either MH. It is a matter of setting it up and seeing if you need one. But, evaporative cooling with a small fan or two can work wonders to stay away from the chiller.> There will not be chiller on this tank, so if you think I'd need one for the 175w halides, I will be going with the 6 or 8 bulb T5HO fixture, most likely the 8 bulb. I suppose I could survive w/o the shimmer. <Well, the T5 will definitely give you the best chance to get away without, but even then you may need one. Although even with 250's you may not need one. It just depends on ambient temperature, evaporative cooling, how close the tank is to a window/sunlight and other equipment such as pumps that may impart heat into the water. It's just hard to say without knowing more specifics of your setup.> Thomas Roach <Welcome, Scott V.>

Re: Lighting.... again/chilling? 9/9/08 OK, well, I'll probably go with the T5. I can't say much about the setup as it doesn't exist yet, we are actually moving to a new house before putting this together, all I have is the tank/stand/refugium so far. But... I have a 200 gallon tank FOWLR which is lit by twin 192w CPF fixtures by Coralife, each with a 10k bulb and a blue actinic bulb. I have a small soft coral in there that is doing extremely well in the upper third of the tank (this came from a small 20g reef tank I was experimenting with but sold to help offset this 65g purchase). We keep our house temperature at about 77 when we are home and 81 when away, and this tank fluctuates between 75 and 85 degrees. (from summer to winter). <In the upper range, but can work so long as it does not fluctuate this much from day to day, just through the seasons.> IMO, those CPF fixtures are hot, even with the little cooling fans built in them. <They get fairly warm.> I was reading more about the power consumption of the halides and am finding even harder to justify them. <Yes, I do like the look, but when all is considered the T5's are winning our more and more nowadays.> Thanks for your input, it has been really helpful. Thomas Roach <Very welcome, have fun, Scott V.>

Lighting Question/Odyssea fixture... Heat/fire concerns  9/1/08 Hello, I have searched endlessly about the new lighting system I have. I recently purchased the cheap Odyssea 48" PC fixture with 2x65w12000k daylight and 2x65w true actinics. Soon after firing them up I noticed they get extremely hot. <PC fixtures can get fairly hot, a subjective observation.> I researched them a little further and read a lot about possible fire hazards and to replace the light bulbs themselves. <I have heard about this over the years, none in a while. The issue was supposedly with the capacitor in the MH ballasts. Some of the stories were plausible, many not so IMO. To my knowledge the PC parts or fixtures never had the issue. Most were changing out the MH bulb due to the poor quality of the bulb rather than the fire issue, the bulbs were not involved.> My question is would changing the bulbs make any difference in the heat being put out? <Not at all.> Also if you do recommend changing the lights what is a good brand. I've heard Corallife isn't that high in quality so please help. <I actually very much like their PC bulbs. There are many other good brands, no one in particular.> Also people recommended changing out the ballasts; is this a good idea as well? <There are never any guarantees with anything electrical, but I would not.> I'm just nervous about leaving the house with the lights on in fear of it burning up and I'm willing to put money in replacement bulbs or ballasts if need be. <Again, I know of no issues with the PC units, but if you are not completely comfortable with running these, then by all means don't.> Thanks! -Sean <Welcome, Scott V.> Lighting, Heat and Ventilation Hi, I'm a newbie to the Saltwater arena and have purchased an Oceanic 72 Gallon Bow Front RR, with canopy. I also purchased the JBJ power compact fixture 48" 65W*4, Formosa -DX. Yes it has a hood. My concern is the heat created in the canopy. The fixture has fans, but there is little room on the ends for air to circulate.  The sides of the canopy (Flexible plastic) do get warm to the touch, but not intolerable. The canopy is open in the back, but that is the only source of air. I have had  suggestions of cutting holes in the end of the canopy, but I'm concerned about damaging it and it's aesthetic value. <Hmmmm, if the unit has fans and was designed for this use, not to worry for it's sake. If heat is an issue, and it well may be, then additional fans, perhaps a raised or suspended fixture may be a better route for you. Look into additional fans and also brackets for supporting your fixture above the tank rim online at one of our sponsors like Foster and Smith. JBJ would be the place to start.> My concern is the heat build up and potential damage to bulbs and fixture. Retrofits really are not an option as the top of the canopy will not support them. <Brackets hold fixture on aquarium rim for support. They make then for 48" fixtures/tanks.  Also, use eggcrate instead of the plastic stuff that came with your tank to increase ventilation.> Any suggestions? My plan is to have corals as well as fish. I know I could eliminate the canopy, but would rather not. Thanks in advance from a "new comer". John <Well, there are several ways. You will find that aesthetics combined with proper and needed function has a price. Poor function is not an option and that's what you have now. There is no doubt that if heat is a problem, something will have to give.   The degree you choose to mix these is up to you and your situation/taste/pocketbook.  Also consider your locale, if your summer weather is hot and you don't have AC, best to open things up and maybe think of a chiller!  Best to start with simple ventilation first!  Craig>

Lighting Fan Help Please: <No problem Steve!> My 125 gallon reef tank is running 84 degrees. I have ordered 2 ice cap 4 inch fans to cool the canopy lighting power compact 72496 retro. Do you recommend that the fans blow into the canopy or out from the canopy? Also, do you recommend that the fans be installed inside the canopy or outside the canopy? <Where they are mounted, inside or out is a matter of taste and where they fit best. Most are mounted inside with the finger guard on the outside. Mount one exhausting and one blowing.> I also ordered an ice cap 4 inch fan to cool the lighting for the ecosystem filter lighting. Should the fans blow inside towards the lighting or blow out from the lighting? Thanks, Steve <Mount it exhausting (blowing out). The incoming cool air will fill the hood from wherever air can fill it. Blowing in is less efficient and cools less. Should keep you cooled a few degrees. Craig>

Lighting I have a lighting question for you. I just bought a custom 120 (used) with no lights. I currently have a FOWLR 75 gallon with only 30 watts of light. The LR has some coralline algae and seems to be doing fine. I really didn't understand anything about lighting until the last few weeks. I have been doing a lot of research. I have read your book The Conscientious Marine Aquarist but still am not sure what to do. Firstly I was bound and determined to go with MH. After learning how hot they get and the cost I decided to move on to another option. <All lighting generates heat, MH's no more than others. <<... no... wrong... RMF... Varying technologies produce a very wide/disparate amount of heat. None more than MH>>  And not that much more expensive initially compared to other lighting options that give the same intensity. One 175 watt MH will cover a 2' x 2' x 2' area pretty completely. To get the same sort of coverage and intensity would require 4 55 watt PC's or 4 75 watt VHO's. MH lamps will go at least one year before replacement is needed, some up to three years. VHO's need replaced every 6-9 months and PC's every 9 months to one year. IN the end, MH's are more cost effective.> Next I was going to use VHO, which also seems to create some heat. Then I decided to just fill the entire hood with fluorescents T-12. Now after reading more you seem to be a real fan of compact fluorescents. What I really would like to do is take your advice directly. The tank is going to be a FOWLR for a little while longer. I would really like to get some good things growing on my rocks before I change over to reef. The lights will be about 2 inches above the water and from the top of the water to the bottom of the tank is 23 1/2". Please let me know also if you think the lights should lay on a piece of glass or if it will be OK for the lights to just sit directly over the water on the 2 glass beams. <You have to follow the manufacturer's recommendation on this point. Some fixtures are ok, other not.> So what is your professional recommendation. I was thinking somewhere along the lines of 440 watts of light with full spectrum and actinic. Thank you. <Any specific recommendation depends on what corals you wish to keep. What is needed for same Yellow Porites would kill many LPS. Decide on this and then look over the FAQ's for any specific recommendations. -Steven Pro>

Lights & Heaters Hi Bob and or Crew: A couple quick questions in regard to lights and heaters. First with heaters I currently have two Visitherm 300 Watt heaters in a 110G reef tank which I would like to move to the sump. Is mounting horizontally a problem with these heaters? <I have never had a problem mounting them this way.> Is this too much wattage for a 110? <maybe slightly more than needed, but they are thermostatically controlled and will not overheat your water. They merely have extra capacity to heat your water if need be.> Would I be better off with two Jager-Jager 200 or 250 Watt (I like the 2MM thickness especially in a sump)? <They are a better product.> Now on to lighting, I am about to buy a Giesemann 2x250 watt metal halide with actinic PCs which I will hang about a foot above the water surface. This light uses the double ended metal halide bulbs which create a very brilliant light but also seem to throw more heat than the common socket metal halide. Any info in regard to these lights and/or bulbs? <I have not seen any comparative info on difference in heat output. These double ended units put out more light than the same wattage single ended lamps. -Steven Pro>

Light vs. Heat Anthony <Anthony is off at the Backer Trade Show. You get Steven this morning.> I just purchased a 260 watt power compact, with fan, for my 110 gallon tank. The unit is raised about 1 inch from the glass which is all the room that I have under the canopy. I noticed that my tank's temperature has risen by 2 degrees in the six hours that the light unit is on. Will this cause any problems for the fish <You do not want the temperature to fluctuate so you may have to use your heaters to maintain a warmer temperature as long as the maximum temperature is 82 or below.> and if so how can I help to dissipate the heat. <The proper use of fans and vents is the easiest way. You want the light fan to be able to blow the hot air outside of the canopy. Else, purchase a second fan to do so and mount it on the back of your canopy.> The canopy is solid on top with airflow coming only from the rear. Thanks as usual. Joe <You are welcome. -Steven Pro>

Light vs. Heat II Steven, A continuation of my heating problem.. I kept my hood open to see if the power compact light was causing the heating problem. (the house temperature was about 79-80* due to a current heat wave) <Pittsburgh has hit 86F today. Strange weather indeed.> The water has not heated up any further so I think that the use of a fan in the hood might be the answer. Which way should the air flow be directed; exhaust or inflow? <Exhaust> The water temperature in my 110 gallon tank is at 83* and has not gone down in spite of air-conditioning the house overnight to 75. The quarantine tank on the other hand only raised to 80* in the heat but went down overnight to 77* and is being controlled by the heater. I am assuming that the temperature fluctuation in the 10 gallon is a lot faster than in a 110. <Correct> How should I go about lowering the main tanks temp or do I allow the cooler house temp to control it and if so how long should I expect it to take. Conversely, it heated up quickly. <If you keep your house at 75, I would think using an exhaust fan would bring the big tank down to 77 in another day or so.> Should I look into the use of a chiller or do you think that the use of the exhaust fan in the hood will control most of the heat source? <If you usually run your AC, I would not worry about the chiller. Even if you keep your house at a modest 78, you should be able to keep the tank at 80.> Thanks again. <A couple more general points. Minimize the usage of powerheads. Much better to use external mounted pumps which dissipate their heat into the room and not into your tank. -Steven Pro>

Lighting (concerns re heat production, elimination) Hi Mr. Fenner, I have a question concerning lighting. My saltwater tank is 60" long x 30" high x 16" deep. The problem is at the top, the middle third has a glass brace across it that is 5/8" thick ( same as the tank sides). <A good idea> How badly will this affect the tank concerning the lighting, since it is already a deeper then average tank, <Actually, the depth of this length/run and volume is a few inches less than "average"> if I want to eventually make it into a reef tank? I know have a FOWLR. I cannot put anything that will heat up a lot. (The top along with the sides are completely enclosed in a custom built cabinet, and it is a see-through to both sides, and already on hot days I have to keep the top door open for heat dissipation, even though my current lighting is way under in terms of sufficient lighting which consists of two 48" fluorescents.)  <Good description> I am currently trying to figure something out to vent the enclosure without any light straying out . <Perhaps some openings on the top with a "light barrier" to allow air circulation, block light... or drilling through the tank, running a clear pipe up through the bottom with cool air... or... > The cabinet is in the kitchen/living room wall, and stray light will not be convenient. A thought: the current enclosure has particle board on the top ( hidden by molding around the edge), if I cut out a big section, and replace it with something heat conductive, such as aluminum, or such , do you think this will make a difference to dissipate the heat up, and out of the enclosure, instead of a fan or such, or will this not make enough of a difference to merit the trouble of the modification?  <Interesting... but don't think this would make much difference> In other words, does passive heat dissipation in this way, work as well as an active design?  Thanks, Greg <Consider the "chimney" approach with or w/o muffin fans to move air over the top and not to worry about the changes in light (some loss of intensity, phase shifting... not too appreciable). Bob Fenner>

I have a question about lighting my 90 gallon reef tank. As of now I have 4 standard 40 watt bulbs and one 30 watt over it. As far as corals go I only have a few polyps which I place as close to the light as I can and they seem to be doing fine , even growing and spreading. I would still like to move up to four 55 watt PC's but I am concerned with the amount of heat that they produce. With my standard fluorescents I am barely able to keep the temperature at 79-80 degrees , I am concerned if I put PC's over it, the temperature might go up even more. I know the extra light would give me more versatility with keeping corals but if they heat up my tank too much I don't know if it would be worth it. How much more would the PC's heat up my tank and would it be worth it to get the extra 60 watts over the tank? Not to mention $300-$400 dollars is a lot of money for an extra 60 watts. Any advice would be appreciated , thank you. >> The power compact fluorescents actually won't heat your water much... probably not even noticeably more than your current lighting arrangement... It takes a lot of energy to raise water temperature. If you find that the heat is too much period in your system, I would encourage you to do two simple things about it: switch the lighting regimen to having the lights on more/all at nighttime rather than day, and look into passive and active venting of the hood. A simple muffin fan cut into the electrical supply to the lights (so it runs at the same time while they're on), or just some holes drilled into the top/sides of the top will lower the temperature a few degrees different. Do agree with you concerning the net gain from the proposed vs. present lighting. If it were me, I'd switch to four 96 watters... FFExpress has them on sale now, I think for $421... or thereabouts. If you think you might go with more small polyp stony corals, giant clams, I'd invest in these instead. Bob Fenner

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