Mirror

[pocilipora]

Can you use miror, cut into a reflector shape, for metal halides. Is there a chart any where that I can look at? Something that compares reflective materials?

[StirCrazy]

a Miror is very reflective but it will also duplacate hot spots as it does not difuse the light at all.. what seams to work good for MH bulbs is a shiny white reflector (ie gloss white paint in your hood, or white sheet metal) or if you can find it hammertone aluminum. if you are talking floressents it would be good as floressent light is already difused so why difuse it anymore.

some people feel that a miror will take away light (because it is going through glass first) but the amount of light that it filters is not realy measurable by our standards but the problem I do find with a miror is that high heat will cause most to delamanate and you will get dark non reflective spots so use on a MH would be short lived because of the heat.


Steve

[Canadian]

Ummm...I call bull$hit on Steve's comment about diffusing MH lighting. Steve, this is one of those cases where your lack of experience in reefkeeping and minimal "research" being espoused as if it is fact, is in fact incorrect and has the serious potential of leading "newbies" astray. Yes, as Richard Harker has pointed out, highly reflective material in conjunction with MH lamps will not do anything to diffuse "hot spots." And yes, the use of a white reflector would indeed diffuse these hotspots. However, a white reflector would seriously diminish the intensity of light entering the tank (when compared to polished materials), and considering MH lighting is not as intense as we would like our lights to be (i.e. in an attempt to replicate the sun), all hobbyists are better off maximizing their intensity and secondarily paying attention to diffusion of light. Therefore, as per Sanjay Joshi's suggestions: use a quality parabolic reflector of some sort in conjunction with MH lighting to ensure that intensity is adequate.

Now, in regards to your question about using a mirror as a reflector: There are two reasons for not doing so: 1) If and or when humid air makes its way behind the mirror, it will tarnish the mirror and it will turn black. 2) Mirrored glass that close to a lamp is at serious risk of becoming extremely hot and could potentially shatter (under a variety of circumstances) due to the proximity and heat of the MH lamp. Clearly, it would not be an especially enjoyable day if you had to pick glass shards and splinters out of your reef tank. And the use of mirrored acrylic and other mirrored plastics is obviously not a possibility as they could melt and become a fire hazard.

With that said, there are a few people who have experimented with the idea of using mirrored tiles glued into their hood thus ensuring no water could contact the back of the mirror. You might want to check on RC (I believe there were a few of them there), and ask them about their experiences.

[reefburnaby]

Hi,

Yah...using mirrors to build a reflector can work...but MH tend to be very hot and they can shatter the mirror if water is splashed on to it. So...it is a bit more risky.

As for the diffuse vs specular, it is your choice. Both will work, but it is much harder to build a DIY specular (shiny) reflector properly than it is to build a diffuse (white) recflector. The white reflector - just bend it in to any shape you want and it will work 95% of the time. While a shiny reflector requires a bit of more planning -- there is a chance that it will be better than a white reflector, but there is also a chance that it is much much worse.

Hope that helps.

- Victor.

[StirCrazy]

Canadian, I am glad we have you here.. what would all us that don't know anything do with out you? damn I am awed in your presence..

I would love to read you book as you seam to know it all.. what is the title?

[pocilipora]

Thanks for the Heated replys, Ive done some reading and I think Im going with the Spyder Reflector.

[Canadian]

The title of my book is "Everything I've Learned From Actual Hands-on Experience and an Education: Things Steve Doesn't Have." You can pick up a copy at Chapters while you're there getting a copy of "English Grammar for Dummies."

Steve, you don't want to go down this road of fire with me...trust me...you'll end up with 3rd degree burns.

[UnderWorldAquatics]

LOL!!!!!!!!!!!!
This is really funny, comon now guys, shake hands and go back to class...

I like parbabolic and spyder reflectors myself, but Ive used the "high heat reflective mylar" when I needed to make something reflective.

[Troy F]

Let's keep it clean guys. I think what touched Andrew off was that a "shiny white reflector" is not "what work's best" and is in fact a poor choice for reflector. I believe either Dana Riddle or Sanjay Joshi stated that a mirror would be the ultimate reflector were it not for the difficulty in application.

I too look forward to Andrew's book, if it is even half as colourful as he is it should be a good read. Of course you could just wait for the movie images/smiles/icon_wink.gif .

[Troy F]

Damn, I was typing my last response and you guys fire off another couple. Be nice damn it.

[terryp01]

Language, please.

[DJ88]

Chris,

If I remember the numbers right I believe that a proper parabolic reflector will increase the light going into the tank by 75% or something liek that. Troy started a thread on this board if I remember right where the numbers are stated. An optimal reflector at J&L is only $46 plus tax. or something like that.

I have a white painted hood and can't have a reflector due to the size of my lid. I will be putting a proper reflector in the 45 when it is up and running. I am positive that I am losing a huge amount of light due to my white hood. images/smiles/icon_sad.gif

[reefburnaby]

Hi,

I am not sure, but I seem to recall Sanjay saying that a spider reflector makes a 175W MH as bright as a 250W MH.

- Victor.

[Gordoe]

I'm almost afraid to post, naaahhh!

You need to keep a few things in mind;

1. You want both visible and "invisble light" reflected.

2. Several things can happen to the light that interacts with a surface. It can be reflected by the surface, just like light on a mirror(Reflected). It can be absorbed by the surface, in which case it causes a change in the temperature(Absorbed or Emitted). In some cases the light can be transmitted through the surface(Transmitted).

R+E+T=1

The reflectors we use have a T of 0. Mirrors that get hot do not have a refectivity of 1, therefore they are absorbing some light.

Polished aluminum has an emissivity(absorption)of 0.05. Paint has an emissivity of about 0.9.

Go with polished aluminum to reflect your lights. If you want to diffuse the light get hammertone, or parabolic.

[One_Divided]

Put an "IME", "IMO" or an "I read somewhere that.." and everyone gets along..

I like to have ideas on reefkeeping and keep my beliefs to the scientific facts. If you don't know for certain that something is a fact, then don't state it as if it is one.

I'd like to add on this and the other current lighting post in this forum.. IME, I have used milar for the whole inside of my hood and after about 9 months, some of the silver just sort of started falling off and left behind clear plastic. Now this worries me, becuase I don't know where that silver stuff went.. I have a feeling it may have corroded by the salt.
images/smiles/icon_confused.gif So I'd say if you are going to use milar, don't cheap out.. Get the highest end you can get.. I think that lighting is an essencial part of this hobby that people too often try to dodge.

[StirCrazy]

Ok I just re read the posts here and I see what caused all this .. I assumed that beacuse a miror was wanted that were were talking about flat reflectors only (my mistake) yes if you can go with a parabolic then that is the best but my opinion was on using a flat reflector on top of your light, and in "My Opinion" I would rather have a reflector that difuesed a point sourse light than a spectral reflector in this instance. the reason for this is if you have hot spots you get burnt plants maybe this is not as important in a reef but, I have been playing with planted freshwater tanks for about 22 years and making my own lights for the last 16.

a good article to read with actual studies on different reflector material is by RICHARD HARKER (http://www.animalnetwork.com/fish2/aqfm/1999/nov/features/1/default.asp)

another statment by Tom Miller

"Glossy white reflectors are also quite effective. A very glossy enameled white reflector can come very close to the same reflectivity of a good mirrored reflector - such as polished and anodized aluminum. Flat white reflectors are less reflective than glossy white reflectors. Non-mirrored aluminum reflectors likewise are not as reflective as highly polished mirrored aluminum. Aluminum is very reflective when polished and protected from corrosion. Aluminum is a very common, less expensive, and high reflectivity coating used on many astronomical telescope mirrors as well."

so I apolagize for any wrong info that might have been derived from my post.

Steve

[Shadetree]

I cannot remember where I read it or even when, I just know that it has been stated that the painted white hood is not much better than NO reflector or paint at all.
http://www.animalnetwork.com/fish2/aqfm/1999/nov/art1101/f11sm.jpg
The graph, courtesy of Richard Harker, can be found in context in the referenced thread above.
This graph shows that it reflects pretty much NOTHING. The second graph goes on to show that it does a little bit to diffuse the light, but if it doesn't reflect any light what good is that images/smiles/icon_rolleyes.gif . I think your second quote is out to lunch, or completely unsubstantiated. Remember the above is glossy painted aluminum flashing, I can only imagine painted wood would be worse. A guy on RC, in this thread http://www.reefcentral.com/vbulletin/showthread.php?s=d483097807b07c50b1d999332cc8e8f3&threadid=55527 found that he got almost 1/3 MORE light with proper reflectors. If you are going to spend the money on halide lighting, I do not see the point of skimping on a quality reflector (DIY is not skimping IF it is made from the proper material).

Scott

[StirCrazy]

here is the other one Shadetree,
http://members.shaw.ca/stircrazy/f12sm1.jpg

this is what I was talking about.. by using white paint or hammer tone or plain aluminum flashing you will not get as much light as using a miror type but you will be able to get a more even and consistant lighting throughout the tank.. but in the same tolken you will not get that high light area whare your SPS will thrive while the rest of the tank is not quite as intence. it is a trade off for what you want I guess, I personaly am using a spectral reflector on my floressent type bulbs and I will use hammer tone on my MH when I get them to TRY get the same intensity everywhare in the tank.

Steve

[Shadetree]

Steve,

What good does diffused light do if it is not reflected back into the tank?

Scott

[DJ88]

Steve,

You lost me..

Why would you want to diffuse the light going into your tank? Any of it. Whether it is NO, VHO, PC or MH??? What are you worried about by having those areas of high intensity where light is stongly focused? Once you sit down for a long period of time and can watch corals and how they react to this lighting you will se why the focused areas IMO are a good thing. We are not even close to re creating natural light levels produced by the sun in our tanks. Not even close. I'd say about 1/10th of the levels. SO any area where focusing happens is a good thing IMO.

Keep one thing in mind through all of this. <ul type="square"> Diffusing results in drastic losses in lighting strength in your tank. Less strength means less penetration into your water. Less penetration means a higher depth for light needing corals where they can be kept into your tank(Corals need to be near the surface) Decrease the light being sent to the corals and you decrease the chances of survival. Period. [/list:u:4342bfe463]

It is the intensity of a MH that allows us as reefkeepers to have many of the coral species in our tanks that we are able to. By putting something in your tank that diffuses the light you have defeated the purpose of maximizing your lighting all together IMO.

Diffusing the light is in effect decreasing it's intensity. Once you do that you have again defeated the purpose behind having intense lighting in your tank. It is only the intesnse lighting of say a MH bulb that reaches the depths of most tanks we use today. NO lighting loses its strength on a massive scale as you go into the water. VHO's & PC's are next for penetration then MH's in it's various forms. By diffusing the light you are reducing how deep the light your corals need so crucially penetrates. A mirrored of polished aluminum reflector is there to get all the light that is being sent in directions other than into your tank and refelcting it back where you want it.

Look at this drawing:
http://members.shaw.ca/montipora/DIY/light.jpg

This is with no reflector. Red lines are full strentgh light beams going into the tank. Orange are diffused light(lower strength). Due to waters nature only light that is emitted from the bulb that results in an angle less that waters critical angle(drawing two) will actually penetrate at full stregth. Anything that doesn't make it within this angle is reflected. losing intensity, diffusing in other words. The light that is sent up to the lid loses strength as it is reflected by white paint and is then useless IMO. Unless it is actually reflected a part of that light is lost due to absorption or diffusion. A big part.

http://members.shaw.ca/montipora/DIY/angle.jpg

When light hits a different medium than air such as water it needs to do so at a certain angle or LESS for it to penetrate. If it is greater than that angle it gets reflected. Once you start reflecting light off of surfaces you lose intensity.

Here is where the parabolic reflector comes in. It gathers the light being emitted by the bulb and sends it in the proper direction to allow for maximum penetration of the water by the maximum amount of emitted light.

http://members.shaw.ca/montipora/DIY/light1.jpg

Personally I'd put reflectors over every single thing I could in my tank. I want every single bit of effective light to go into the tank. If I could go mirrored I would. But I can't. So Polished metal it is.

[ 14 February 2002: Message edited by: DJ88 ]</p>

[reefburnaby]

Hi,

IMHO, it really does matter if the light is distributed using a specular reflector or a diffusive reflector. The main idea is to get light from the bulb in to the tank and both do the job. You'll just have to design the reflector to do the job correctly. In other words, a specular reflector doesn't look exactly the same as a diffuse reflector.

So, in terms of white vs shiny, white and shiny do a very good job at reflecting visible light. The difference between white and shiny is that shiny reflects other types of waves (like gamma waves, x-rays, infra-red and etc) and white doesn't do a very good job at that -- hence white paint's high emmisitivity. Emmisitivity is a measure of how much electromagnetic waves a material will absorb -- visible lilght is only a small band in the electromagnetic spectrum. Since our application involves concentrating visible light in to our reefs, then shiny and white should preform similarly (with the upper hand to shiny...since 100% pure white and mirror flat surface is hard to obtain with paint).

Specular and diffuse refectors have their problems. Diffuse refectors tend to spread their light even across the reef -- this may be problematic if you are try to raise light loving corals. Specular reflectors tend to concentrate their light on to specific bands within the reef. IMHO, this can be problematic because certain parts of the reef aren't well lit and some are too well lit -- so coral placement will be key.

One point that I haven't seen in papers is that white reflectors do get hotter than shiny ones. This is because white does not reflect infra-red very well. This may be a good thing since we can remove the heat from the white reflector with fans. On the other hand, a shiny reflector would deflect the IR waves in to the water and warm it up. It is much more difficult to remove the heat from the water...

So...there's my take. Both methods are fine. The design of the reflector must take in to account of the advantages and disadvantages of each method.

Hope that helps.

- Victor.

[ 14 February 2002: Message edited by: reefburnaby ]

[ 14 February 2002: Message edited by: reefburnaby ]</p>

[Reefmaster]

so i'm curious victor, is it likely white reflectors are also absrobing a bunch of the longer wl's as well? i don't think i know why white would absorb IR but not UV. simply a function of the wl?
either way this thread has gotten me to thinking i want a new reflective media in our hood.
shane

[reefburnaby]

Shane,

White paint have been engineered to reflect all visible light -- hence the colour white. However, each blend/brand of white paint have no guarantees as to what it will do to IR, UV and other waves -- unlike shiny metals (almost guaranteed). Without being specifically engineered to reflect IR or UV, the paint is mostly likely going to absorb all or some of it (engineers/chemists tend not to overdesign images/smiles/icon_wink.gif it is a hard enough problem as it is )

Hope that helps.

- Victor.

[ 14 February 2002: Message edited by: reefburnaby ]</p>

[Canadian]

Just an FYI, using fans to cool the air temperature in your hood (eg. blowing fans at your reflector or lamp) as opposed to using fans blowing onto the water's surface to effectively control temp is not one of the best ideas. Cooling the air temperature around the lamp will cause a shift in the spectrum emitted by the lamp. Everyone hates 5500K lamps because they're too yellow, so why would you blow air at your reflector or 6500K lamp therefore causing the color temperature to decrease if you could avoid this arrangement?

Those who actually have experience with MH lighting (incl. HQI) over their reef tanks know that they purchased the lamps and ballasts in an attempt to maximize intensity. Making any effort to diffuse that intensity in an effort to get even distrubution of a lower intensity is clearly counterproductive if you intend to keep light-loving corals alive and healthy. Your only recourse should you choose to diffuse your point source lighting (still can't figure out why on earth you'd want to do that in your reef tank) would be to purchase additional lamps and ballasts in an attempt to compensate for the lost intensity -- go nuts if you've got the money to waste.

I'd like someone to point out to me what the problems with focusing specific bands of higher intensity artificial light into your reef tank are. Before these higher intensity point source lamps were available hobbyists struggled to keep SPS, Tridacnids, etc. alive with diffused light sources, let alone thriving. "Too well lit"? What is it that we're attempting to replicate? The sun? Is the sun overlighting the ocean?

If you want to have evenly distributed light over the entire surface area of your aquarium while also having sufficient intensity to keep light loving corals, put more lamps over your tank.

[ 14 February 2002: Message edited by: Canadian ]</p>

[Aquattro]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>this arrangement?

I'd like someone to point out to me what the problems with focusing specific bands of higher intensity artificial light into your reef tank are.

[ 14 February 2002: Message edited by: Canadian ][/QB]<hr></blockquote>

Andrew, as I'm sure you are aware, glitter lines from MH lighting are speculated (proven?) to enhance SPS growth due to the focused intensity of the light. This confirms that focused light not only isn't bad, but probably benificial. I have to agree that after spending all the dollars to install MH lighting, the last thing I want to do is diffuse it!!

[DJ88]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>that is if the corals want more light. However, if your precious SPS coral sits between a bright band and a no/low light band (assuming no glittering), then half of you SPS is not doing well...and the other is doing very well. In other words, there is a chance that half the SPS will actually starve. I know this is an extreme example and it rarely happens because....
<hr></blockquote>

Won't happen.. Have you ever had the surface of your tank perfectly calm ALL the time? I haven't, Not with proper circulation in your tank you won't. Those "glitter" bands you see will move. Show me a tank where they don't move and I will show you a tank with not enough circulation.

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote As for the cooling thing...we could try blowing at the the reflector from side, but not at the bulb.

Why? Blow it at the waters surface and you will get the best cooling results through evaporation. Those running MH's or any high heat lighting in your hood will find this out. The amount of cooling you will get through cooling the reflector is so minimal in comparison to what you get from evaporation it is a waste of time and energy IMO IME. I have tried it. I am running the fans to blow across the H2O and will in any future systems. I recommend it to anyone running MH or experiencing heat problems in a tank.

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quoteThose who actually have experience with MH lighting (incl. HQI) over their reef tanks know that they purchased the lamps and ballasts in an attempt to maximize intensity.

Yup. As I measure it on my new little light meter my MH produces about 20,000 lux(quick measurement). When I read direct sunlight it hits many, many, many times this amount. I just measured it at 62,000 lux outside with clouds and smog. That is three times the amount of light outside with clouds than my MH produces at 12" away. Why would you want to diffuse it and make it less than that? The flourescent lamps in my elevator produce 300 lux for a reference point for those who don't have MH or have never ran a MH.

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quoteMaking any effort to diffuse that intensity in an effort to get even distrubution of a lower intensity is clearly counterproductive if you intend to keep light-loving corals alive and healthy.

For those who still want to do this, read my last statement. We are many times BELOW what the sun puts out into the ocean. WHY???? would you want to diffuse it????? You are putting your corals at risk. In effect you are giving them LESS chance at being healthy.


<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quoteYour only recourse should you choose to diffuse your point source lighting (still can't figure out why on earth you'd want to do that in your reef tank) would be to purchase additional lamps and ballasts in an attempt to compensate for the lost intensity -- go nuts if you've got the money to waste.

I can't understand the point of diffusing something that is supposed to provide point source lighting???? Agree 100% here.

If you want to diffuse your lighting and then compensate with more bulbs or lamps go for it. Most here are trying to save money where they can by DIY'ing the ballasts etc. You are shooting yourself in the foot by reducing what those lights put out with diffusing IMO.

[ 14 February 2002: Message edited by: DJ88 ]</p>

[Troy F]

Good post Darren.

One thing that I came upon in my reefboard wanderings was Jerel's lighting schedule. He runs his MH in short bursts and is experimenting with increased growth with less light. Basically, he points to the amount of energy a coral must use to protect itself from the UV radiation and is trying to find the line of balance where there is actually too much light in regards to growth. The point where the coral begins expending more energy protecting itself than growing. This would be an expensive endeavour however, as you would seriously jeoprodize the life of the bulb. He offsets this by using electronic ballasts and being rich (apparently). I realize this is a little off topic. My reason for posting this is that our closed systems don't mirror images/smiles/icon_smile.gif the real world for a number of reasons.

[One_Divided]

I just had an idea.. In our reef tanks, our bulbs are totally stationary. Aside from the shimmering cuased by halides, there are without a question, spots (cuased by shadows) that would end up getting very little light compared to other spots. In nature the light source (the sun Duuhh) rotates and therefor would light most corals from almost every angle possible over the course of a day. Has anyone ever thought of the idea of light movement? It could be tricky and expensive, but if done in the right way might actually save money. If a bulb could start on one end of the tank and end up at the other side by the end of the day then most areas of the tank would be hit by light. For example, using 1 1000w halide instead of 3 400ws.

I don't know, I could just be talking out of my a$$, but it's just an idea.. Now the hard part is inventing the machine that moves the bulb from side to side.. How about roatating in an oval? images/smiles/icon_eek.gif

[StirCrazy]

this is something that a lot of fanatics do in planted fresh water tanks Adam, I was at a web page whare a guy has a 400 watt MH bulb slowly start at one side of his tank and move across over the course of a day to the other side of the tank on a motorized track. he also had hidden floresent lights for ambiant (sp) light.
If I can remember the page I will get you the link.

Steve

[Canadian]

Adam, "they" make them. Lighting tracks of the type you describe are used in hydroponics and they have been used in reef aquarium applications as well. The inherent problems with them are: huge cost, size, and the potential for any mechanized device like that to seize up when mounted in close proximity to the evaporated water coming from an aquarium (among other things).

But if you're really interested in implementing the idea take a look on RC and reefs.org; there have been a few people with "high end" set ups who have incorporated that kind of an idea into their setups.

[Canadian]

Troy,

I'd be interested to see Jerel's results. The potential exists that while he may experience increased coral growth (skeletogenesis), he may also experience color changes in his corals. As of yet (at least to the best of my knowledge), the debate regarding what causes color changes in corals has not been resolved. I know that Richard Harker has commented that his ability to use natural sunlight on his new reef set up has caused many of his darker colored corals to move from brown shades to more tan shades, and that the other pigments (blues, pinks, etc.) have intensified. So while corals may in fact have to expend energy to protect themselves from prolonged exposure to high energy light waves, that same protection may be what causes the corals to manifest the colors that we desire . . . might be a slippery slope where we have to choose which of the two evils we prefer.

[reefburnaby]

Hi,

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr> Won't happen.. Have you ever had the surface of your tank perfectly calm ALL the time? I haven't, Not with proper circulation in your tank you won't. Those "glitter" bands you see will move. Show me a tank where they don't move and I will show you a tank with not enough circulation.

<hr></blockquote>

Glittering only shifts the light by a limited amount. There will always be a case where a specific area in your tank is not as well lit as others.

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote Why? Blow it at the waters surface and you will get the best cooling results through evaporation. Those running MH's or any high heat lighting in your hood will find this out. The amount of cooling you will get through cooling the reflector is so minimal in comparison to what you get from evaporation it is a waste of time and energy IMO IME. I have tried it. I am running the fans to blow across the H2O and will in any future systems. I recommend it to anyone running MH or experiencing heat problems in a tank.

Well...that wasn't quite what I was getting at....I was talking about the fact that shiny reflects warm up tank water faster than white reflectors. The heat that isn't transfer to the water is stored on the painted reflector -- which can be removed by fans (think of it as a heatshink).

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>I can't understand the point of diffusing something that is supposed to provide point source lighting???? Agree 100% here.

If you want to diffuse your lighting and then compensate with more bulbs or lamps go for it. Most here are trying to save money where they can by DIY'ing the ballasts etc. You are shooting yourself in the foot by reducing what those lights put out with diffusing IMO.

<hr></blockquote>

Reflector design is still more important than diffuse vs specular. A well design diffuse reflector would outperform a poorly design specular reflector -- regardless if it is a line source, point source and a diffused source.

- Victor.

[ 14 February 2002: Message edited by: reefburnaby ]</p>

[Troy F]

Andrew, I hear you. If light intensity does turn out to be the primary cause of the "brighter" pigmentation then I don't think there'd be any decision to make. I'd give up a little growth for the nicer colours. The context of the information I was "quoting" images/smiles/icon_wink.gif from was more for achieving maximum growth at the best returns (least energy). Really I've added nothing useful to the conversation. Just added a poorly conceived point about the differences between nature and the captive system. Must shut-up now.

[reefburnaby]

Hi,

I would agree that focusing light for corals is a good thing -- that is if the corals want more light. However, if your precious SPS coral sits between a bright band and a no/low light band (assuming no glittering), then half of you SPS is not doing well...and the other is doing very well. In other words, there is a chance that half the SPS will actually starve. I know this is an extreme example and it rarely happens because....

Did you know that the spider reflector actually spreads the light out rather than focusing it ? If you do a ray trace, you'll understand what I am talking about.


BTW, diffuse lighting doesn't suffer from the depth effects as much as spot/specular light -- its a waveguide phenomenon with respect to the water and the glass walls (okay...that's getting really technical...). So...its a bit more tricker than one would think.

As for the cooling thing...we could try blowing at the the reflector from side, but not at the bulb. If there is a will...there is a way images/smiles/icon_smile.gif Besides...its the intensity that counts ? right ?

- Victor.

[ 14 February 2002: Message edited by: reefburnaby ]</p>

[DJ88]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quoteGlittering only shifts the light by a limited amount. There will always be a case where a specific area in your tank is not as well lit as others.

The glitter lines in my tank shift quite a lot. It is noticeable enough that it is almost hypnotic. With proper circulation and movement of the water in your tank you get a fair bit of light movement throughout the area of the tank being covered by the MH. The gliter lines don't sit still that is for sure. The surface water in my tank is very convoluted and moving constantly. Which also moves the lines of intensity constantly.

And of course there is areas that aren't as well lit as others. If you want the same coverage throughtout put multiple lights and/or a reflector to focus the light. This will also be dependant upon the shape of your tank.

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quoteThe heat that isn't transfer to the water is stored on the painted reflector -- which can be removed by fans (think of it as a heatshink).

It is a heat sink. But removing that heat from it isn't nearly as efficient as putting a fan that is hitting the waters surface. I have tried. And had planned on doing this on my next tank until I found the best way to remove heat was not to hit the reflector with a fan but blow air across the water.

As an aside unless you had the fan directly(within a few cm's) of the reflector it, like water out of a pump, loses velocity which will aid in cooling. Once you get any distance away from the reflector the speed at which the air is passing over the reflector and pulling away the heat stored is minimal. IMO. On my 45 with a 24"x24" hood I may get some benefits from this. On anything larger I don't see it benefitting heat removal. Even with my smaller hood, I will still go with the fan on the water. If it works better(more efficiently) why not use it?

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quoteReflector design is still more important than diffuse vs specular. A well design diffuse reflector would outperform a poorly design specular reflector -- regardless if it is a line source, point source and a diffused source.

I know that but my point with the statement

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quoteIf you want to diffuse your lighting and then compensate with more bulbs or lamps go for it.

was if you are specifically buying point source lighting to get the intensity that corals need and thrive on, why would someone want to diffuse it?????? If you are going to waste the money like that send it my way. images/smiles/icon_rolleyes.gif

All you need to do is look at this graph.

http://www.animalnetwork.com/fish2/aqfm/1999/nov/art1101/f11sm.jpg

Look at how reflective white paint or flashing is. Then look at aluminum. I can't imagine how much light I am losing as I HAD to go with white paint. I can't wait to throw that reflector sitting in my new tank on and measure the lumens again. Nuff said.

Anyone still want to diffuse point source lighting? Send me the cash you were gonna spend on MH and I'll send you some NO ballasts. Equal trade IMO. images/smiles/icon_rolleyes.gif

[ 15 February 2002: Message edited by: DJ88 ]</p>

[StirCrazy]

Darren, don't take this wrong but I think you need to reed the definitions of Specular reflectivity, and Diffuse reflectivity. from what you are posting it sounds like you think Diffuse reflectivity doesent reflect at all. this is just wrong.. actualy here is the definitions for all to see Oh there is also Spread reflectivity which is kinda a mixture of both..

"Specular reflectivity is the type that occurs in a mirror or any other highly polished surface. In the case of specular reflectivity, the angle of the reflection is equal to the angle of incidence. When we look into a mirror, the objects we see are at the same angle to the mirror as the angle at which we are looking at the mirror. Spread reflectivity is similar to specular reflectivity, but the reflected light is more scattered about the reflected angle. Diffuse reflectivity, as the name implies, is reflectivity where the reflected light is spread in all directions. An example of a diffuse reflector is a white painted reflector."

now havign said that... which one is better.. it totaly depends on what you are doing.. if you are rich and can afford lots of MH bulbs then go for the "Specular reflectivity" ie. spectral alumium (which is what I am using for my floresents) but if you can only aford say 1 MH for a 3 foot tank or 2 for a 5 foot tank you might be better going with a "Diffuse reflectivity" type reflector like hammer tone or good forbid white painted flashing. images/smiles/icon_smile.gif the idea is to spread the light over more of the tankto get a even lighting and make due with what you have. I have seen tanks that are realy bright in one area and dim in another becuse they coulden't aford enuf lights and quite franky it looked bad IMHO.

I know you have enuf lights that you don't have to worry about this and by the sounds of it most estableished reef people on this board do also.. (Andrew when are you going to host a meating so we can get a chance to see your tank?) but for people who are putting togeather new systems and want to spend more money one substrates and skimmers and such, or are not planning on keeping SPS for a while a "Diffuse reflectivity" type reflector might be the best bet, keep in mind I do not avocate the painting of the inside of your hood to make a reflector becaus it is just plain flat and won't work as good as if you bent up a piece of white flashing.

to see what I mean take a small piece of "shiny white flasshing, and a miror. go to a dark room and shine a focused been of light into the miror so it reflects onto the wall.. then do the same with the flashing.. the circle from the flashing will be a lot bigger than the one made by the miror, yes it will be less intense but it will give a larger area the same amount of even light. enuf said about that.

Also I think victors idea of blowing the back (or side) of the reflector instead of the water surface would be good if you wanted to cut down on the evaporation rate.. the more air yyou have blowing at the surface the more evaporation you have. So by cooling the reflector you will drop hood temps which will also help to lower your tank temps.

Steve

[Canadian]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>to see what I mean take a small piece of "shiny white flasshing, and a miror. go to a dark room and shine a focused been of light into the miror so it reflects onto the wall.. then do the same with the flashing.. the circle from the flashing will be a lot bigger than the one made by the miror, yes it will be less intense but it will give a larger area the same amount of even light. enuf said about that.
<hr></blockquote>

Wheew....took a while but I finally made sense of that.

Ok Steve, now that you've admitted that the intensity would be diminished with a diffuse reflector, ask yourself this: "Is my goal to be able to keep mushrooms alive in every square inch of my tank, or is it to be able to have sufficient intensity to keep SPS alive and thriving?" Per unit area, a specular reflector will provide more available light.

Sorry, can't have a meeting to see my tank; I don't have one at the moment (I think you might have been one of the few people who didn't know this. I answered lots of questions about this at the last meeting at Victor's). I sold my tank to Darren in the summer so that I'd be able to focus on my edumucation and not have to choose between neglecting my tank and excelling at school (don't want to have to be a stoker). However, I'm sure you knew this before you suggested I have a meeting so you could see my tank. You were apparently trying to be a "smart ass" but it went right over my head, as I'm accustomed to your stupidity.

When the temp goes up to 25 degrees Celsius in the summer try blowing (un air-conditioned) air at your reflector to cool the water temp as opposed to using evaporative cooling...let me know which one works more efficiently for keeping the water temperature down.

[StirCrazy]

Ahhh their is the Anderew we all know and love..
I wasn't trying to be smart.. I am a stoker and acording to you there is no way I could be smart, and I was serious when I said I would have loved to see your tank, and yes I was probable one of the few that didn't know that you didn't have one.

Steve

[Canadian]

Steve, if you honestly weren't trying to make a backhanded comment, then I apologize publicly for being a jerk; I was out of line with what I said. I think I'm more irritable that usual (guys like Troy who've seen my normal behavior over the years know that I'm "ornery" but not usually this bad) being that it's midterm time right now and I'm stressed out. Maybe I vent that stress and frustration here, and I really shouldn't do that. Here's what I'll do: I'll take a break from the board until my midterms are finished and see if I'm less of a jerk when things have calmed down.

Once again, I apologize to everyone on the board for my poor behavior, and especially to Steve.

[reefburnaby]

Hi,

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr> It is a heat sink. But removing that heat from it isn't nearly as efficient as putting a fan that is hitting the waters surface. I have tried. And had planned on doing this on my next tank until I found the best way to remove heat was not to hit the reflector with a fan but blow air across the water.

<hr></blockquote>

Well...couldn't you put it on both ? Both water and reflector ? images/smiles/icon_smile.gif I don't have HIDs, but I have heard that blow air at both water and lamps helps reduce the water from heating up too much. Just a suggueston...

As for the diffuse vs specular, I guess we'll need your light meter to settle this. You measure 20,000 lux....how far away from the lights was this ?

- Victor.

[DJ88]

Victor,
<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quoteWell...couldn't you put it on both ? Both water and reflector ? I don't have HIDs, but I have heard that blow air at both water and lamps helps reduce the water from heating up too much. Just a suggueston...

Here are some quotes from elsewhere in the thread that hopefully will answer a few things in your question.

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quoteIt is a heat sink. But removing that heat from it isn't nearly as efficient as putting a fan that is hitting the waters surface. I have tried.

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote Just an FYI, using fans to cool the air temperature in your hood (eg. blowing fans at your reflector or lamp) as opposed to using fans blowing onto the water's surface to effectively control temp is not one of the best ideas. Cooling the air temperature around the lamp will cause a shift in the spectrum emitted by the lamp. Everyone hates 5500K lamps because they're too yellow, so why would you blow air at your reflector or 6500K lamp therefore causing the color temperature to decrease if you could avoid this arrangement?

These were found due to peoples experience with MH lighting. HTH

[Rainman58]

I used mirrored plexiglass in my canopy which contains 3 X 150 watt MH, 2 X 110 watt fluorescents and 4 X 40 watt fluorescents and have had no discolouration or melting at all. My canopy is 14" deep with the fluorescents mounted approximently 1" from the plexiglas and the MH mounted 5" away from the plexiglass. I`m also running two 4" Icecap fans (one at each end of the canopy) for cooling with 2 1/2" holes drilled in the lid for ventilation. This seems to work pretty good and i`ve never had a problem with my water temp rising above 80 degree`s.