# How to keep Temp down with Higher lighting?



## ngb2322 (Apr 9, 2008)

Right now I have 130W compact flourescents and a 32W weak sauce light that must go. What I want to do is get into the 200-250W range, but do it myself. There is a DIY post here: http://www.aquaticplantcentral.com/...iy-70w-hqi-metal-halide.html?referrerid=20987
for a 70W metal halide that I am going to try. I will put two of them in with the 130W compacts. However, I am already having temperature issues with the tank rising higher than the set point on my heater (I try to keep the tank aroun 75F for some Kuhlis, its going up around 80-82). I currently have my lighting sitting on top of my glass canopy. My idea is to make a hood that keeps the lights about 3-4 inches above the water level and leave an open back on the hood and have two fans to release heat. Also, I will probably remove the glass canopy which should allow more heat to get out. Anyone have any advice on keeping the temperature down with higher lighting?

Unrelated question, will moonlight (I would like to incorporate some LEDs in the hood) adversely affect plant growth?


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## ruki (Jul 4, 2006)

re: heat build-up

That can be tricky. I have this problem in Summer. I have a number of plant tanks, so as the room heats up, it becomes too warm for the aquariums to shed their extra heat into. I don't really want to spend the extra money for extra air conditioning for this room, but that would do the trick. If the room is cool enough, the aquariums will want to drop closer to room temperature.

Brute force is to get a chiller, but this costs serious electricity and heats the room up even more. If you can put the heat exchanger part outside of the fishroom, then vent that heat outside it starts to make some sense. Otherwise, you end up cooling the aquarium but heating up the room and then spending more electricity to air condition the room...

Leaving the top off allows for evaporative cooling, but that also contributes to room humidity. My stuff is in the basement, so that's totally unproductive. Yeah, you can run a dehumidifier, but that heats the room up some more and ...

I decided to try a low-light, low heat room since my cool water loving plants (moss, etc.) and fish can't handle the heat in the bright room. That should work better, I hope.

P.S.
Don't think that moon lights would interfere with plants too much. Probably no effect at all since they wouldn't be bright enough to grow plants on their own.

I think you a simpler problem though. As long as you don't have to worry about humidity and you don't have racks of tanks in the room, I'd see if evaporative cooling would do the trick.

Hope this helps a bit.


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## reefcrawler (Dec 31, 2007)

Metal halide will bring up the water temp. dramatically, I had the same problem, it's ended to switch to a PC light.
and it's impossible to keep 75 in my area (S. CA), unless you have a chiller/vent system.

I'll also always suggest to leave the top open as "ruki" suggest, I've thrown away the glass top since the first day of purchasing the tank.

the other walk around, helpful but not efficient way - use a fan to blow on the water surface can also lower the temp. 

to build up a sump and work with "fan" (or chiller mix with a vest system) is more practically so can hide the fan from main display tank... but comes with some investment.


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## ngb2322 (Apr 9, 2008)

Thanks. First thing I think is to lose the glass canopy and see how that works. Humidity shouldn't be an issue. Chillers cost too much and I don't think I need one anyway, I usually run the AC in my apt. at 70 during the summer (in PA, summers aren't toooo bad). I'll try that and see how I do. Thinking about it, I might just return the 130W and get a 260W flourescent that has two fans built in and legs that keep the light obo 3 inches above the water. That would save me a ton of time.


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## nopain00 (Jun 12, 2006)

I had similar problems when I upgraded my lighting hood. I have a 65g in an NYC apartment that gets very hot during the summer. I've tried the evaporative cooling methods as well as venting the lighting hood. Both work to some degree but the bottom line is that if the surroundings are hot, then the tank is never going to drop much in temperature.

I ended up just getting a chiller. I know they are expensive but if you keep an eye out on eBay or craigslist, sometimes a cheap one shows up. Even though I wasn't happy about spending the money to get one, looking back it was a great investment. Now, I never have to worry about the temperature. I just set it and forget it. It really gives me peace of mind if I go away for a while during the summer. I no longer come back to cooked fish.

My best advice is to look at the temp. difference between the room in the summer, and your target temperature of your tank. If the room is the same temp or hotter, then your tank will likely never get cooler since passive cooling through evaporation is not very efficient.


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## lauraleellbp (Jan 31, 2008)

Have you considered switching to T5HOs? T5HO fixtures stay much, much cooler than PC or MH fixtures due to 1) their efficiency and 2) the bulb configuration stays much cooler. I could feel my 260watt PC fixture from across the room. I can put my hand on top of my 216watt T5HO fixture and it's just warm. Heat during the summer is a serious issue where I live, too. They're also more space-saving than PCs if you're DIYing a fixture. I know they're pricey up front, but the bulbs last 3-4x as long as PC bulbs, which ends up saving $$ very quickly.

Moonlights are pretty cool and there's no reason they would adversely affect plants.


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## ummyeah (Apr 8, 2008)

> Have you considered switching to T5HOs? T5HO fixtures stay much, much cooler than PC or MH fixtures due to 1) their efficiency and 2) the bulb configuration stays much cooler. I could feel my 260watt PC fixture from across the room. I can put my hand on top of my 216watt T5HO fixture and it's just warm.


We went through this on TPT. Stop posting false claims when you don't know how it works. T5HO's are less hot because they use individual reflectors. They have slightly more lumens per watt but the credit is due to the reflectors. You use less bulbs due to the reflectors. A 65 watt PC is 24" while a 54 watt T5HO is 46". Obviously a T5HO would *feel* cooler since it disperses heat over 46", but once it's on the tank it's all the same. A 400 watt MH puts out as much heat as 400 watts of T5. The heat will still go in the tank no matter how long the bulb is.



> Heat during the summer is a serious issue where I live, too. They're also more space-saving than PCs if you're DIYing a fixture.


How are T5HO's space saving when they're longer? That is why PC's stand for Power *COMPACT* or *COMPACT* Fluorescent.



> I know they're pricey up front, but the bulbs last 3-4x as long as PC bulbs, which ends up saving $$ very quickly.


T5HO's with proper cooling should last roughly 18 months or 1.5x a PC and that's going by *REEF* terms. Planted tanks are much less picky.


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## lauraleellbp (Jan 31, 2008)

Yes, Umm and you're no more correct here than you were there, unfortunately. I have no desire to repeat a pointless conversation and stand behind the points I made, other ppl can draw their own conclusions.


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## ummyeah (Apr 8, 2008)

We don't need opinions we need FACTS. The point to this conversation is to help other people make smart descisions, not hand out infomation that comes off the top off our heads.


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## hoppycalif (Apr 7, 2005)

Most of the "science" of growing aquatic plants is made up of opinions, not proven facts. Each of us has formed opinions based on our own experience, our study of what we find here and in other forums, logic (as we see it), etc. So, to insist that everyone stay mute unless they have scientifically proven facts to dispense is to ask that the forum be shut down.

So, rather than attack someone else's "facts" or "opinions", doesn't it make better sense to provide your own "facts" or "opinions" and do a good job of convincing us that yours are better than his? I think it does.


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## ruki (Jul 4, 2006)

ummyeah said:


> We went through this on TPT. Stop posting false claims when you don't know how it works. T5HO's are less hot because they use individual reflectors. They have slightly more lumens per watt but the credit is due to the reflectors. You use less bulbs due to the reflectors. A 65 watt PC is 24" while a 54 watt T5HO is 46". Obviously a T5HO would *feel* cooler since it disperses heat over 46", but once it's on the tank it's all the same. A 400 watt MH puts out as much heat as 400 watts of T5. The heat will still go in the tank no matter how long the bulb is.


Stop correcting people when you don't know how it works either. :lol: T5HOs are more efficient and less hot in part because they don't waste energy by shining light at themselves across tube bends. Reflectors are important in sending light in a desired direction, but aren't included in the bulb output numbers where potentially you might want to illuminate in many directions. (The fact that T5HO have much better reflectors than Power Compact compounds their effectiveness in sending light downward into the tank at a high angle.) Data on T5HO is readily available since it's a standard. Power Compact is difficult to look up online and has variations in tube diameter, drive current, shape and end connectors. Some PC bulbs also appear to be overdriven to get additional brightness, but this further reduces their efficiency. T5HO tubes are rated at 92 initial lumens per watt and this dips into the upper then mid 80s as the tube ages. Many, if not most, Power Compact tubes are not rated -- go figure!

Metal Halides are more complicated. The pulse start bulbs have gotten much better lately, but still are less efficient then fluorescent for low wattages. 400 watts is about the crossing point though. A good 400 watt bulb initially does better than T5HO, but then is worse at mid life. I think it makes the most sense to use MH for huge tank with a larger than 400 watt bulb allowing you to fully take advantage of the efficiencies. You can see this pattern in medium wattage MH bubs at http://www.lrc.rpi.edu/programs/nlpip/lightinganswers/mwmhl/pdf/table1.pdf



> How are T5HO's space saving when they're longer? That is why PC's stand for Power *COMPACT* or *COMPACT* Fluorescent.


Power Compacts are great for length restricted applications. But for longer length applications they are not optimal. A 4-foot long T5 HO fixture is quite small and is significantly more efficient in getting light down into the aquarium than a thicker Power Compact fixture of the same length. They also can be placed in a rack where you don't have to as much clearance above the fixture due to heat concerns. For me this space saving over Power Compact.



> T5HO's with proper cooling should last roughly 18 months or 1.5x a PC and that's going by *REEF* terms. Planted tanks are much less picky.


Why should T5HO bulbs behave differently for a reef tank than for a planted tank? I'm assuming the same fixture since it' not specified. This looks like unsubstantiated opinion to me 

I have to agree with Hoppy on this one. It's really tough to insist on pure facts. I don't think you met your own requirements. So this reply was mainly an illustration that it's counter productive to insist that everyone always provide substantiated facts.


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## ummyeah (Apr 8, 2008)

You incorrect about MH. MH is very, very efficient. T5HO can't come close to a 250 watt and would be a nightlight to a 400 watt. You're basing you claims on specifications according to commercial applications which is entirely inaccurate. Hang out on RC and look for GrimReefer and Sanjay.



> Stop correcting people when you don't know how it works either. T5HOs are more efficient and less hot in part because they don't waste energy by shining light at themselves across tube bends.


I don't know how it works...okay? You are referring to restrike, which is adding on to what I said. Who wouldn't know that? Yes, T5HO is more efficient due to it's linear design but it is still a fluorescent. Don't over exaggerate with tall tale claims like it is the sun in a bulb.



> than a thicker Power Compact fixture of the same length


They're the same width, 5/8".



> pulse start bulbs


Have you heard of electronic ballasts? They're more efficient.



> due to heat concerns


They're the same thing! They're both 5/8" tubes in different shapes. 400 watts of PC gives off the same heat as 400 watts of T5.



> Why should T5HO bulbs behave differently for a reef tank than for a planted tank? I'm assuming the same fixture since it' not specified. This looks like unsubstantiated opinion to me


Corals and clams require much more PAR and thus the bulbs need to be replaced more often.


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## ruki (Jul 4, 2006)

You don't get it. I wasn't really interested in arguing. The purpose of my post was pointing out that you are demanding an impossible standard. People just don't think that way...

With such a standard you need numbers, not just what two people say on a internet BBS. At least I gave numbers.

Did I state like "sun in a bulb". Stating false quotes from others makes one factual?

The term restrike is means the minimum length of time you have to wait to re-power up the bulb after it's been shut off. If one demands facts one should get the lighting terms correct.

Take a closer look at the Coralife Quad tube 96 watt PC fixture. It's not the same 5/8ths width, it's thicker than that. (Not all PC bulbs have the same thickness.)

You also managed to contradict yourself. If MH at 400 watts is so much more efficient than T5HO, then it must give off less heat not the same. Think about it.

I'm not the one who demanded the factual accuracy, but after you demanded it and got stuff wrong it proves it's an impossible standard. 



ummyeah said:


> You incorrect about MH. MH is very, very efficient. T5HO can't come close to a 250 watt and would be a nightlight to a 400 watt. You're basing you claims on specifications according to commercial applications which is entirely inaccurate. Hang out on RC and look for GrimReefer and Sanjay.
> 
> I don't know how it works...okay? You are referring to restrike, which is adding on to what I said. Who wouldn't know that? Yes, T5HO is more efficient due to it's linear design but it is still a fluorescent. Don't over exaggerate with tall tale claims like it is the sun in a bulb.
> 
> ...


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## Tex Gal (Nov 1, 2007)

Ummyeah, you really sound angry. I don't know why. I'm sure you are trying to be helpful but you come off curt and bossy. We are all trying to help here. I don't have studies to back up what I say, just opinions based on my experience. When people help me here I expect that what they say is IMO too. Like Hoppy said we are all just trying to help. There are so many opinions, even with the experts. 

You just sound angry....


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## trag (Jan 9, 2008)

hoppycalif said:


> So, rather than attack someone else's "facts" or "opinions", doesn't it make better sense to provide your own "facts" or "opinions" and do a good job of convincing us that yours are better than his? I think it does.


Hoppy makes good sense. So here's some facts. But first some pontificating.

Both of the main contestants here seem very emotionally infested in their technology. Why not analyze the choices for what they are and then accept them as they are? This is harder to do after you've already purchased some lighting systems because of a bizarre little human phenomenon known as cognitive dissonance--which basically translates to: none of us can stand to admit that we've made a bad decisions so anything we've invested time or money in must be the best thing ever.

Anyway, first, 400 watts of light does translate to 400 watts of heat, regardless of the technology. There are minor variations, because some of that energy is radiated by the fixture as heat and so may escape upwards rather than into the aquarium. For example, a distant ballast will radiate some heat that doesn't reach the aquarium. But in general, it doesn't matter what light technology you are using, 400 watts is 400 watts.

However, light technologies vary in efficiency. So 400 watts of one type of light may be equivalent to 350 watts of another type of light. So, if both lighting systems put out the same amount of usable light, and one uses 350 watts and the other uses 400 watts, obviously the 350 watt system is going to heat your tank less while still providing the same amount of light.

MH lighting does not compare to T5HO at 250 watts. The cross over point is at about 400 watts. Below 400 watts MH light is considerably less efficient ranging down to about the efficiency of old T12 magnetic ballast fluorescent lighting at 70 watts. And the light output of a given bulb does drop off vastly sooner than with T5 HO.

When one writes that MH will blow T5HO out of the water, I can only assume that the author is confusing light intensity with energy efficiency. MH is more intense in terms of light output per square inch, than T5 HO. No doubt about that. It is also less energy efficient, producing less total light per watt of electricity consumed.

See my posting here: http://www.aquaticplantcentral.com/forumapc/science-aquatic-lighting/34149-proper-wattage-aquariums-3.html#post368021

The most efficient (usable light per watt input) lighting system currently is T5 normal output. There may be something more efficient in a lab somewhere, but in terms of what you can buy off the shelf, that's it. It's about 10% more energy efficient than T5 HO, But it is also about 2/3 as intense (light per square inch).

The most intense (light output per square inch) lighting available is high intensity LED lighting, which is outside the price range of most of us. However, HI LED is less energy efficient than even old style magnetic ballast fluorescent. Second most intense commonly available light source is MH.

So, when choosing your lighting, 400 watts of energy consumption by the lights is likely to be 400 watts of energy put into the aquarium. But some light systems require more than 400 watts for the desired level of light, and some require less than 400 watts for the desired level of light. My posting above will allow you to calculate rough equivalencies between the different light technologies.

I have not specifically addressed PC lighting, because as one of the earlier posters wrote, there just aren't good figures available on it. It is less efficient at delivering light to aquariums than T5HO and if the geometry works for using T5HO, then that's generally a better choice. On the other hand, the kits and reflectors from AHSupply are mighty nice and make their PC retrofits an attractive choice even with the loss of efficiency.

I hope that helps. Of course, the WWW being what it is, it will probably just further fan the flames, but that's okay.


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## fredyk (Jun 21, 2004)

Such language! My apt gets hot and my tanks gets hot as well. 

Some plants die, for example, EC, downoi, creeping jenny, and mosses, although peacock moss seems ok.

opps! edit:
alot of plants are ok. vals, crypts, hair grass, many others do ok even in very hot apt!


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## ummyeah (Apr 8, 2008)

The Myth of MH being hotter than T5s.

What is your test setup for MH and T5?



> 400 watts of light does translate to 400 watts of heat


400 watts of MH would equal the heat output from 400 watts of T5HO. All the tests that are done comparing the the two are unequal. T5's have IceCap reflectors and ballasts. MH have a white background or a cheap parabolic reflector on a magnetic ballast with a cheap 20000k bulb. Put an Iwasaki with a Lumenbright or Lumenarc reflector on an IceCap ballast. Then show me tests. We'll see the results when Sanjay Joshi on RC is finished.


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## TortoiseBoy (Dec 30, 2004)

I am trying to wrap my brain around your point about a watt being a watt, trag. Is the assumption that, regardless of the path it takes, the energy put into the tank via light is going to end up as sensible heat?

There are two things that are tough for me to figure out. First, doesn't it make a difference that some lighting systems are able to put more of the energy they consume directly into light vs. that energy being lost to heat right away? For instance, doesn't it make a difference that when I touch some ballasts, they are very hot to the touch whereas when I touch others they are relatively cool? If the ballast is warmer, more energy went toward heating it and not toward lighting your tank, correct? 

It seems to me that the system that doesn't spend a lot of energy on "waste" heat would allow you to get more light into the water than a system that puts out more "waste" heat. This would allow you to get away with lower wattage and therefore less heat in the tank and in the room. Am I correct on this? Therefore, it seems that debates on how efficient lighting systems are might be more complicated than "a watt is a watt." Again, I don't know, I am just asking 

The second thing that is confusing to me about the "a watt is a watt" argument is that it seems like wavelength plays a role, here. As an example, I was thinking of the sun's energy. Relatively short-wave energy is intercepted by the Earth's surface, but it is not until the energy is absorbed by the surface and re-emitted as relatively longwave energy that heating occurs. This is why the hottest time of the day is not at solar noon but a couple of hours later in the day. Re-emission must catch up with solar radiance. So, I was thinking that the fate of the energy pumped into the tank has something to do with what happens to a watt of energy. Low-angle light just bounces off the surface of the water without ever penetrating (that's why reflectors are so important), some light go into the water and scatters, some is absorbed by the water, some bounces around one or more times, some is intercepted by the substrate or plants. Is the assumption that it will all eventually be converted to heat, regardless of how many steps it takes the light to get to that point? 

Finally, (and here is where I get back to the original thread topic!) I think there is a difference between looking at the heat that escapes to the room in general vs. the light that generates heat in your tank before ever getting out to the room in general. My tank has an enclosed canopy and I have two 12-volt fans in it to keep it cool. You had better believe that if the fans are not working, there is a large difference in temperature in my tank vs. when they are working. So, watts that go to heat inside the canopy of my tank or heat generated by penetration of light directly into my tank are different than watts that just go out into the room in general and heat the tank by convection, advection or radiant heat. 

Once more, I say that I am pretty sure my thinking is wrong on some of the above. I would appreciate it if some of you big-brained folks (trag or others) could help me understand. Thanks again and great thread!

TB


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## trag (Jan 9, 2008)

TortoiseBoy said:


> Is the assumption that, regardless of the path it takes, the energy put into the tank via light is going to end up as sensible heat?


That's the assumption. It is not a terribly good one, but it is good enough. A ballast might take 10% of the energy, but in general, virtually all of the energy is going to make it to the light bulbs of whatever type.

There are several things going on at once.

1) All the light which gets into the tank ends up as heat eventually. Some part of it may be trapped in chemical bonds by live plants and so does not end up as heat--at least not until it rots...

2) A lot of the light which doesn't get into the tank ends up as heat in the tank, because it heats the environs of the hood which directs the IR into the tank.

3) The escaped vs. captured light isn't going to vary that much from setup to setup, so for purposes of rough comparisons of different light technologies, it is good enough to say that it is all heat. Also, for comparison purposes, you wouldn't compare one technology with a great reflector vs. another technology with a poor reflector.

4) If you are trying to do an energy budget for your aquarium of how much heat goes in from lights, filters, etc. vs. how much heat escapes from conduction, radiation, convection, then no, I would not simply take the light wattage number except as a rough estimate. But for comparison purposes, a 400 watt light is going to add about twice as much heat to a tank as a 200 watt light regardless of what technology each light is using.



TortoiseBoy said:


> If the ballast is warmer, more energy went toward heating it and not toward lighting your tank, correct?


Maybe. First, yes some ballasts are less efficient than others. Energy which does not go to the bulbs, comes out of the ballasts as heat. But temperature of the ballast is not a good method of comparison of ballast efficiency unless all other things are equal. For example, a ballast with a low specific heat casing will seem hotter than one with a high specific heat casing (though it will take longer to burn you for a given temperature). Also, convective cooling of the ballasts may be different in different circumstances.

So, yes, different ballasts will consume different amounts of energy at the ballast, but it is generally a small enough percentage of the total, and the percentage from ballast to ballast is close enough, that it can be ignored when talking about light technology in general. Now, once you have your technology picked out, by all means, find the most efficient ballast you can.



TortoiseBoy said:


> It seems to me that the system that doesn't spend a lot of energy on "waste" heat would allow you to get more light into the water than a system that puts out more "waste" heat. This would allow you to get away with lower wattage and therefore less heat in the tank and in the room. Am I correct on this?


Yes. I addressed this in my previous message when I pointed out that one light system might put out as much light using 350 watts as another does using 400 watts. You get the same amount of usable light, but the lower wattage system adds less heat.



TortoiseBoy said:


> Is the assumption that it will all eventually be converted to heat, regardless of how many steps it takes the light to get to that point?


Yes. Unless the light actually escapes the environs of the tank, it is going to end up as heat in the aquarium system. Open hoods are more likely to allow reflected light to escape. But in an enclosed hood, eventually the bouncers end up as heat, which is pretty likely to be IR which goes into the tank. When comparing different technologies of light production, we can ignore the effects of escaped light by assuming it is about the same percentage for each technology.



TortoiseBoy said:


> Finally, (and here is where I get back to the original thread topic!) I think there is a difference between looking at the heat that escapes to the room in general vs. the light that generates heat in your tank before ever getting out to the room in general.


There is some difference. But for comparison purposes it doesn't make a lot of difference. Also, unless you're planning to put a calorimeter around your tank and take measurements, such ballpark comparisons are the best we can do.


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## lauraleellbp (Jan 31, 2008)

I appreciate the discussion now being held- IMO there's big difference between a discussion and an argument and I really don't enjoy the latter.

A friend of mine over on TFH's forum put these lights to the test himself and measured PAR- these were his results:

"You will see the difference right away that a PC lamps is a poor substitute for lighting that is intended for photosynthesis. 

I have taken readings in the same tank at the same height and just changed the fixtures and came up with this data...
PC 260w=PAR 180
T5 HO 2X54w=Par 370
MH 150w 10,000k=Par 300
MH 250w 10,000k=Par 525
Standard output 40w lamp=Par 86

On systems of T5 HO with 4 bulbs or more PAR met or exceeded 500!
All depths were 18" 

I hope everyone understands that T5's are much more powerful of lamps. Kiernon's constant analogy of a T5 is a straightened out PC lamp was not accurate. Everything from color spectrums, efficiency, and types of ballast are different! Finally, individual reflectors will increase efficiency further. "


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## BryceM (Nov 6, 2005)

OK,

The OP posted a reasonable question. The discussion had turned a bit ugly there and I'm glad the tone of the current conversation is better.

I'll risk offering my opinion here and I'll try to stick with what I know. Trag makes some good points and AFAICS he's correct.

I use 450W of MH light and another 156W of T-5 light over my 180g tank. During the 11 hour photoperiod there is only a 1 degree F rise over the morning temp. Granted, big tanks don't heat up as quickly but this is without any fans or chillers. The trick is to use an open design that maintains an air gap between the fixtures and the water surface. A light fixture (of any type) sitting directly against a glass cover heats up the tank VERY quickly. I use an open canopy that allows for free circulation of air out the top and out the back. Pendant fixtures accomplish the same thing. If this isn't an option for you, fans blowing across the surface or even around the fixture will be of enormous benefit.

Now, on to point number two. Assume a particular light fixture uses 100W of power. The power is "consumed" in various ways. The balast uses a percentage. Feel them. They'll be warm. Some will be lost in the wires (very little). Some is converted to light (after all, that's what we're paying for). What is left over is generally lost as heat. A fixture that is 100% efficient would produce no heat at all, since all of the energy would be converted to light.

No currently available fixture is able to do this. Incadescent and halogen bulbs convert almost all of the electricity to heat (~90%). Light is produced, but not too much. They're enormously wasteful.

Flourescents and MH bulbs are better, but still, only about 25-40% of the energy is converted to light.

MH fixtures use very small bulbs. As a result, the surface temperature of the bulb is tremendous. Touch one sometime and you'll probalby leave a bit of skin behind. Flourescent bulbs are enormous in comparison. Roughly the same proportion of energy is lost to heat as with MH, but it is distributed over a large area, causing most of us to assume that not too much heat is produced. The actual difference in efficiency between the two is insignificant when dealing with overtemp issues.

Don't get me started about the comparison betwen T5, VHO, HO, T8, T12, and CF's. The technology is all the same. Newer designs get more of the light into the aquarium (T5's with good reflectors), but all of these designs still loose at least 60 or 70% of the original energy input as heat.

You can argue the merits of PAR and actual efficiency of each type of setup. If you assume that 100W of T5 is equal to 50W of CF then you can use half as many bulbs to accomplish the same effect. Is this true? Probably at least a little. It's still debatable. So much of it depends on reflector design, bulb choice, etc. Carefully designed control studies are hard to come by.

So what can you do about heating? (Keep in mind this issue is not equivalent to a discussion about light efficiency). Mount the ballasts remotely. Provide an air gap that will allow heated air in the vicinity of the fixutre to rise, carrying the heat away from the aquarium. Use fans in enclosed fixtures to accomplish the same effect. When all else fails, use a fan blowing across the water (evaporative cooling), or give in and buy a chiller.


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## TortoiseBoy (Dec 30, 2004)

Great stuff, folks. This stuff is very interesting to me.

Lauraleellbp, that is some interesting work that your friend did on PAR. It seems like the bulb may have a lot to do with the PAR equation, though, and the bit that you sent didn't specify that. I think that even with the optimal bulb in place, though, PC wouldn't be able to come close to T-5. This is what I was interested in because I have PC and T-5 on my tank ;-) Very interesting.

Trag, thanks for taking the time to explain it to me. I think I get it better now.

Guaiac_Boy, I like the points that you made, as well.

Thanks to all of the posters for taking the time to post.

Here is what I have gotten out of this discussion that might be of practical value in terms of building a system that heats the tank as little as possible for a given amount of light:

1) All energy put into the tank turns into heat. Therefore, all other things being equal, you need to minimize the wattage of lighting to reduce heat which brings us to...

2) Efficiency. The better the conversion factor of energy to light, the less heat we are putting into our tanks (given a specific light level goal). I still think that this is arguable to a large extent based on different system parameters, so I feel that the T-5 vs. MH vs. Others debate is still worth pursuing. 

3) It matters WHERE the heat (especially the waste heat) is. I am a geographer, so of course it comes back to a spatial problem ;-) If you are trying to minimize the temperature of the water, it really matters greatly where the heat in the system is and how much can be transferred directly to the water. If (like in my sorrily designed setup), all of your ballasts and lights are in an enclosed space, the heat will get into your tank much more efficiently (a bad thing, in this case). If, however, your ballasts are isolated (good idea, Guaiac_Boy) from your canopy, or you have fans to move the air, or you don't have a canopy at all, then the heat can be transferred more efficiently to the room at large. This is a good thing and is where the "watt is a watt" can be mitigated a bit. Energy that is transferred out of the local area of the tank, will not contribute nearly as much to the heating of the tank. Once the energy is out in the room at large, it is part of a different system with its own set of feedback mechanisms (such as, typically, a house-wide or local heating or cooling system on a thermostat). 

4) Let's put this discussion into perspective a bit. People grow some great plants in some awesome-looking tanks using any and all of the lighting methods that have been discussed in this thread. The comment on cognitive dissonance is a very good one. We are all attached to the method(s) that we have spent money on because we don't want to think of ourselves as having made foolish purchases. So, use the info from the smart folks in this thread (this rules me out) and try to apply it to your NEXT lighting setup. In the meantime, bask in the knowledge that, whatever you have chosen in the past, it has worked for you and therefore was a worthy purchase!


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## trag (Jan 9, 2008)

lauraleellbp said:


> Kiernon's constant analogy of a T5 is a straightened out PC lamp was not accurate. Everything from color spectrums, efficiency, and types of ballast are different! Finally, individual reflectors will increase efficiency further. "


I am not familiar with this argument. However, a couple of factors to consider are that Compact Fluorescent lamps are the same technology as T5HO. However, the strange geometries and multiple nearby tubes typically used increases restrike resulting in a loss of efficiency. They may take this one into account when specifying the spectrum of the bulb, but the output spectrum of fluorescent lights changes with temperature.

So, if the folded configuration of the PC lights lends itself to greater heating of the bulb, then the frequency spectrum output by the bulb is going to shift as the temperature changes.

If you have a bathroom fan/light/heater combination, try installing a screw-in PC bulb some time. Now turn on the light, note the yellowish glow. Now turn on the heater for 20 minutes or so. Note the bluish glow of the light. This only works if the heater heats the light fixture when on.

But with 50%+ of the light emitted away from the tank, there's a huge margin for the reflector to work with. Depending on the reflector used, PC can be more efficient than T5HO. In theory, T5HO should outdo PC. But the reflectors can make or break that higher efficiency.


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## ummyeah (Apr 8, 2008)

lauraleellbp said:


> I appreciate the discussion now being held- IMO there's big difference between a discussion and an argument and I really don't enjoy the latter.
> 
> A friend of mine over on TFH's forum put these lights to the test himself and measured PAR- these were his results:
> 
> ...


Can you please tell me the setup of the MH?


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## lauraleellbp (Jan 31, 2008)

I've asked him to post some specs so I'll let ya know when he gets back with me.


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