2x150W DE MH vs 6x54W T5 Dilemma

[Navyblue]

I am putting together a 4'x2'x2' tank. I might run a 5"-6" of DSB, but I have not decided yet. I'll also have a sump roughly about 2.5"x1.5"x1.5".

I intend to keep soft corals, mushrooms or anything else that doesn't consume calcium (no calcium reactor yet, dosing is too time consuming for me). However, I'd like my lighting to be able to support SPS or clam in the upper part of the tank or so, just in case that I do any of them in the future.

I know that I can't be wrong with MH. But I live in tropical region. Using MH will requires some sort of cooling measure. I hope that I can get away without chiller due to space, aesthetic, noise, and power consumption constraint. Using fan will induce lots of evaporation which I find it too time consuming too to top up water everyday. But if I really have to go down the MH path I'll get a chiller, though I prefer not to.

I have never ran a T5 system before. I know that T5 will definitely be cooler than MH. But due to the closer proximity to the tank, will it (say may be 6x54W) still be significantly cooler than 2x150W DE MH?

Also, will 6 tubes of T5 be suitable for need described above?

Thanks for reading. :)

[Ti]

Do the T5

[Navyblue]

So I guess 6 tubes of T5 is decent enough for most SPS and clam at the top 6" or so?

[Navyblue]

Btw, I intend to have 4 white and 2 blue tubes.

[michaeldaly]

If it were me, I'd go for the MH.

[RichConley]

If you're going to do MH, ditch the 150s, and go for 175s, and run Iwasaki 15ks.

[pjf]

The Light Research Center lists 93 lumens per watt for 46” daylight (3K-6.5K) T5HO (54-watt) lighting (http://www.lrc.rpi.edu/programs/nlpip/lightingAnswers/lat5/pc1a.asp). The luminous efficacy may go down for higher color temperatures.

The luminous efficacy figure for a 150-watt HQI bulb is harder to come by. My guess is ~70 lumens per watt for shielded HQI. There are variations with manufacturer, ballast type and spectrum.

This means that for the same wattage, the 6x54w T5 fixture produces ~30,000 lumens and the 2x150w HQI fixture produces ~20,000 lumens.

When you factor in the more efficient reflector for the smaller HQI bulb, I think that you will get as much usable light from the HQI fixture as you would from the T5HO fixture. This is especially true if there are no individual reflectors for each T5HO tube. If so, the comparison is a wash and you should not immediately dismiss the HQI fixture.

If you live in a tropical area and have air conditioning, you may not need additional cooling. I frankly think that a large T5 fixture mounted close to the tank may hurt air circulation.

[Ti]

I would say MH, but probably easier to do t5, you can do sps and clams with that set up.

[MaximumPuffer]

i like MH's because of the shimmer effect they produce on the sandbed and you probably wont need a chiller if you mount the bulbs 8 inches or more above the tank.

[Navyblue]

Thanks guys for your responses. I used to run 150 W of PC then switched to 150 W DE MH, the temperature did spiked for a good couple of degrees. But my tank noticeably looked a brighter. So somewhat I got the feeling that watt per watt, MH would always pack more punch than fluorescent (though I have to say that I've never used any T5).

[Grey Reefer]

Don't underestimate T5's. With the right reflectors T5s are usually more potent than a MH setup. Remember T5s use less electricity, bulbs don't need to be replaced as often, and don't spike heat in a tank as bad as MH. Just my .02

[newreefbishop]

mmmmm....so many opinions I might as well give mine. Its basic math when you look at at. MH may "seem" to run hotter. Remeber you have one buld that is generating a massive amount of energy, a byproduct is heat. Now you take a T-5, granted the light is diffused along the length of the tank, which is a good thing, but heat is generated along the length of the tank...you have a large area of heat generation a larger surface to cool. With a MH you have a single point to cool. Its much easier to manage heat, IMO. The second issue is energy use. how can 6x54watt bulbs a total of 324 watts use more electricity than two 150 bulbs....for a total of 300 watts.

I am not knocking t-5s because I love them but the bottom line is its a case by case basis, I live in south florida and Im going 175 halides this weekend....I have heat issues yes, but its easily managed, with fans....and if I want to take it a step further I will get a chiller....just that simple. Reason being the basic makeup of a halide put it at a step higher than any t-5, PC...etc. Reason being out of the box with a basic reflector you will get light going to the bottom of the tank.....and the much loved shimmer effect.

With a t-5 though bright after 24-25 inches its not recommended. And if you want to use it to that depth you have to use expensive german reflectors that try to match the MH's intensity.

Some people actually take it a step further and say well MH are more expensive....but it seems to balance out to me. By European standards, t-5s should be changed every 8-12 months...American standards tend to push a bit further....but in any case if a bulb costs 25 dollars...(average) and you have 6 bulbs....thats 150. Two 10k Ushio 150's are 47 dollars a piece....so your looking at 94 dollars....basic dollars and cents....

Once again on a case by case basis it will work...but I love MH.

[plumb]

I agree, go with the mh but if you want sps id get the 250 watt de and mount them higher over the tank. you will upgrade to higher wattage so you might as well start there. you can always have t5s as filler lighting, but alone they WILL NEVER GET THE SAME GROWTH RESULT AS THE MH. (for sps)

[hahnmeister]

Id go with T5s for one major reason... color. Im just finding that my corals are responding more to the output and the color combinations I can get with T5 bulbs. Running halides alone often leaves you with all your hopes in one bulb, one color, etc. If this bulb doesnt have a full range (and if you are running them alone, they will more than likely be 14-20,000Ks that lack much of the warmer spectrums all together), you might not get the growth and coloration you desire. With T5s, you can mix and match to get the look 'just right'.

At that, I would have to say that 150s or 6x54watters might not be enough. I would consider dual 250s or 8x54wattT5s for a 120g (4x2x2). OR, the best solution is a little bit of both. The best looking/growing tanks I know of happen to be a few 120g tanks some friends of mine have with 2x250wattDEs running 10,000-14,000Ks and 4x54wattT5s running blue+ bulbs and actinic+. The look is very different, like a 'day-blue'... almost not quite natural, but it works very well. The corals all 'pop' more than any other lighting I have seen... the pigmentation is intense and glowing.

As for MH vs T5, all of the research I have been doing stacks them up against each other 1:1. HO T5s top out at about 85 lumens/watt, and halides top out at about 105. The thing is, the halides lose much more of their output as they get bluer. Just going from 3000K to 6500K takes a decent chunk out... not to mention 10,000K and 14,000Ks. T5s have an easier time generating blue light thanks to their phosphors. But the real advantage of T5s, esp with aquariums, is how they get that light into the tank.

The T5s generate a very even light field across the entire top of the tank. The lack of 'shimmer' is actually an indication of their better penetration, being a linear source rather than a point source. Now I know that that might make some people gawk, thinking that nothing penetrates like a halide, but its true. The output might even be higher overall, but the package that halide comes in is its greatest short-coming. Halides are more of a point source, and so rather than carrying their intensity as far, they have a higher peak towards the top as you get close to the bulb. Many 20,000K 250watt halides generate PAR levels in excess of 2000 close to the bulb, while a T5 generates a little less than half of that... as its more spread out. This means that with a halide lit tank, you get those two 'spotlights' at the top where the light just under the water surface CAN be very high. The thing is, for most halides, due to heat and light distribution, we raise the bulbs off the water surface a good 6-10". Well... that takes away that peak that haldies are so good at. T5s, OTOH, can sit right above the water, and so even though they might only make half the output towards the top... that extra 3-6" closer to the tank helps alot. And then there is the angle of the light. Most of the light from a T5 reflector is angled to enter the water at a relative perpendicular angle to the surface... and what light the water surface does refract is better caught by the T5 reflectors which cover more of the water surface. Then look at the halide... unless you are directly under that 10"x12" reflector you may have, the light is entering the water at an angle, and this boundary makes all the difference. Even going from just above the water surface to just under, while being directly under the reflector can cut a good 200 PAR right there. Now, consider all that light around the edges of the halide reflector that has to enter the water at an angle... much of it gets refracted back up. Ever look inside a halide and a T5 canopy and compare how well lit the inside of the canopy is? The halide lights up the canopy almost as well as the tank, and the T5 canopy... well... its pretty dark in comparison. This is also why lumenarcs work so well, but between the two, T5s just do a better job generating blue light, and they do a better job getting the light they do make into the tank. The T5s, being closer to the tank than a halide, can generate the same peak levels at the top (around 550-600 PAR), across the whole top (not just the spotlit areas), and that light then penetrates deeper than with halides.

Heat wise, Id say T5s are worse though, from a certain standpoint. Thermaldynamics says that what goes in, must come out, so if a light source makes less light with the same wattage, the rest of that energy must be spent on something... heat. The conception is that T5s are cooler... well... they are at any given point. But thats because you have 250watts spread out over a 18 linear feet of 5/8" diameter tube. A 250wattDE has only 4" of 1" tube to shed that heat. Put both in a calorimeter, and the heat output would be very similar. At that, keep in mind that a 250wattDE is really about 320-350 watts. I would also compare the output of 234 watts of T5 to a similarly color matched 250wattDE bulb... with a slight edge going to the T5s distribution wise. I found more problems this last summer with my T5 lit tank though with regards to heat. The T5s will be getting their own fan, much like the halides, for next summer. As long as you think about fans/ventilation in the planning of the tank, either one can easily be kept under control heat-wise. I have used nothing more than evaporative cooling (fans blowing across the water surface) to keep my tanks at 80-82 degrees... and Im talking no more than 40 gallons of water (no sump) being lit with a 250wattDE halide in a 90degree room. The specific heat change of water as it goes from liquid to vapor takes alot of therms with it.

[Navyblue]

Thanks guys for all your wonderful inputs, though I'm not sure if this is bringing me closer to making the decision. :D

Ok let's view it from another angle. My main reason to go for T5 is that I might get away without a chiller or fan. If the T5 are not that cool and I need a chiller or fan anyway, I might as well go for the MH.

So the question of the day: Does any of you managed to run any T5 tanks in a hot summer without fan or chiller? Without turning the tank into a fish pot of course. :p

[Grey Reefer]

Either one your going to have to run fans on. hahnmeister hit the nail on the head though. Because you can mix and match bulbs you can get the exact corals you want and/or coloration of colors. Plus if you stare at T5's they won't burn a hole in your retina like MH will (not that I do that:hmm5: ) There are combo fixtures out, like the Maristar. Current-USA just came out with a nice looking one too.

[newreefbishop]

hahnmeister, well said....

[newreefbishop]

Personally I plan on running a mix of halides and t-5s....which would be the best bet..... 10k bulbs on the halides....

[Navyblue]

I do like the spectrum aspect of the T5, but right now I am leaning towards the MH as it seems to be a little cheaper.

I wonder if 2x54W HOT5 actinic is going to make any visible difference to 2x150W DE MH 10000K.

[jimmy595]

No matter what the light, if you dont have the tank in an a/c room during hot summer months your going to have heat problems. I would think fans would be more effective at cooling t5's than metal halides. If you plan on doing T5's plan on adding fans (supposed to increase output by 20% as well). MH you could get away with placing 8" above the tank w/out fans.

[Navyblue]

When using fans for T5, do you mean to have the fan blowing the light to cool down the tubes or to have the fan blowing across the water surface to induce evaporation? Or both? I don't mind as long as it doesn't cause excessive evaporation that would require me to top up FW everyday.

[pjf]

I agree that T5s have a very even light field and that MH bulbs can produce a spotlight effect. However, more light is lost from T5 tubes than from MH bulbs.

In a dark room with only your MH light on, see if any “glitter lines” pass through the glass of your aquarium and land of your floor or walls. These glitter lines represent light “leakage” where total internal reflection (TIR) has failed. If you place your eye where the glitter lines pass through your tank, you should be able to actually see the MH bulb. This bulb is typically the one at the far end of your fixture.

In a typical MH aquarium, there may be glitter lines that pass through the upper portion of the side glass but not the front or back. This is because if a ray of light strikes the water within 60-degrees of vertical, it will be refracted downwards at an angle that will cause the glass or acrylic walls to reflect it back into your aquarium.

Now try a similar experiment with your tube lighting. Place your eye on the glass just below the water level. If you can see the distant T5 or the distant ends of the T5 tubes, there is light leakage instead of TIR.

There are two ways to ensure that MH lighting is totally internally reflected instead of lost. The first is to use a reflector that embeds the bulb deep inside. Examples are Lumen Arcs and DE bulb reflectors. The second is to raise the bulb so that its height is at least half the horizontal distance to the glass. For example, if your tank is 16 inches from front to back, raise the MH bulb so it is at least 4 inches above the water. These measures ensure that the light strikes the water within 60-degrees of vertical.

What I’ve described to ensure TIR with MH lighting is impossible with tube lighting. You will always have T5 light leakage through the walls of your aquarium.

[hahnmeister]

The T5s may cost a little bit more to begin, but the long term operation costs are less than with halide. The bulb replacement costs are better. The better T5 setups that cool the bulbs better, and use better bulbs can get you that 2-3 years from that $20 T5 bulb... halides are pretty much over at a year, maybe 2 if you are using 10,000K DE bulbs. The energy savings are possible as well (okay, I have seen 154 watts of T5 kick 250watts of halide butt before, but that was because the T5s were GE 6500Ks and ATI blue+ bulbs... two of the best performing bulbs out there for T5 reefs). And I would stack 234watts of T5 against my 250wattsDE, and as it turns out, the 234 watts of T5 is really about 240-250watts, and the HQI is really up around 320-350. And when you stack up bluer halides, like 14,000Ks and 20,000Ks the output gets cut alot. I dont think I would consider running just 2 250wattDE bulbs on a 120g if they were 14,000-20,000Ks... its just not enough light IMO. You would be lucky to get PAR levels of 100 at the bottom... barely enough for open brain corals and some shrooms. The only way I would do dual 250s alone is if you like the 10,000K look (which hey, thats how Sanjay does it). If you really want dual halides alone, the best option IMO would be to use dual 400s with a nice 400watt bulb like a Ushio or Aquaconnect in dual lumenarc3 reflectors... but $$$ per bulb. I used to be a fan of this, but like i said before... your options for tweaking the spectrums are nil. Often times I have found myself wishing I could just change a little bit of something about a halide bulb... a little more actinic and daylight in my pheonix bulbs, or a little more blue in my ushio 14,000Ks, or a little more yellow/red in the XM 20,000Ks... and there is often no bulb that is 'just right'. With T5s, if I want to swap out one aquablue 11,000K bulb for a 6500K bulb to bring out the reds and yellows a little more in the corals, I can do that. With halides it means looking at a whole new bulb, and possibly a whole new setup. I find the T5s more versitile, and of course, a combo of the two, thats the best.

[hahnmeister]

<a href=showthread.php?s=&postid=8809428#post8809428 target=_blank>Originally posted</a> by jimmy595
No matter what the light, if you dont have the tank in an a/c room during hot summer months your going to have heat problems. I would think fans would be more effective at cooling t5's than metal halides. If you plan on doing T5's plan on adding fans (supposed to increase output by 20% as well). MH you could get away with placing 8" above the tank w/out fans.

I run w/o AC in that room during summer. Water can be kept at about 80 degrees in a room that is warmer than that simply through evaporation. IMO, fans are all you need, and also, halides are easier to keep cool than T5s... somewhat. Like I said above, the T5s and halides make about as much heat overall, the halides are just more concentrated. The cool part about being concentrated is that it leaves all the rest of the area open for fans to blow across the surface. T5s can be a little tricky... trying to cram all that extra airflow in between a 2-3" space between your lights and tank.

[hahnmeister]

<a href=showthread.php?s=&postid=8812349#post8812349 target=_blank>Originally posted</a> by pjf
I agree that T5s have a very even light field and that MH bulbs can produce a spotlight effect. However, more light is lost from T5 tubes than from MH bulbs.

In a dark room with only your MH light on, see if any “glitter lines” pass through the glass of your aquarium and land of your floor or walls. These glitter lines represent light “leakage” where total internal reflection (TIR) has failed. If you place your eye where the glitter lines pass through your tank, you should be able to actually see the MH bulb. This bulb is typically the one at the far end of your fixture.

In a typical MH aquarium, there may be glitter lines that pass through the upper portion of the side glass but not the front or back. This is because if a ray of light strikes the water within 60-degrees of vertical, it will be refracted downwards at an angle that will cause the glass or acrylic walls to reflect it back into your aquarium.

Now try a similar experiment with your tube lighting. Place your eye on the glass just below the water level. If you can see the distant T5 or the distant ends of the T5 tubes, there is light leakage instead of TIR.

There are two ways to ensure that MH lighting is totally internally reflected instead of lost. The first is to use a reflector that embeds the bulb deep inside. Examples are Lumen Arcs and DE bulb reflectors. The second is to raise the bulb so that its height is at least half the horizontal distance to the glass. For example, if your tank is 16 inches from front to back, raise the MH bulb so it is at least 4 inches above the water. These measures ensure that the light strikes the water within 60-degrees of vertical.

What I’ve described to ensure TIR with MH lighting is impossible with tube lighting. You will always have T5 light leakage through the walls of your aquarium.

I disagree. I can show how T5s get more of their light into the aquarium rather than in the room due to their larger reflector area and better creation of perpendicular rays to the water surface. The amount of light that halides lose before even getting the light into the water is much greater than with T5s because of the angle that the water must enter the water and get refracted. I dont see how the light, once in the aquarium, from a T5 would be any worse than that from a halide. If anything, the light from a T5 would be more parallel to the glass... top to bottom, due to its linear dispersion field... where a halide has a more spherical or cone shaped dispersion field due to it being more of a point source, causing more leakage at the top. And those glitter lines are not just created at the top of the tank, they are a sign of a point source of light being interrupted by the waves in the water surface. While your tank might have more 'shimmer' at the top, many other tanks do not... the shimmer lines are created as the light disperses, and often across the sand. The reason you have more shimmer lines at the sides of a tank is because the reflector. The area directly under the bulb and reflector fills in for itself very well, so a ripple in the surface doesnt cause the 'shimmer' as there are other light rays present to fill in. The glitter, or shimmer lines are usually from the light that enters the water surface at an angle, to the outside of the reflectors edges. Its a sign of a point source of lighting, not of internal reflection. As for raising the halides to 4" or more... well... most people here would consider that too close in the first place. 6-10" is more the norm. And while rescessing the bulb is somewhat of a good idea (although already a given with most halide pendants), making the reflector wider (like a lumenarc) to help spread out the light better results in better dispersion, which results in better penetration.

[pjf]

If you disagree, try my procedure. With your eye against the glass and just below the water level, try to see your T5s. If you can see them, the light has passed through the aquarium and is lost. You will always be able to see a part of the T5 array. Therefore, the rays from the T5 cannot be perpendicular to the water.

Properly mounted and reflected, you will not be able to see a MH bulb through the glass and water. Total Internal Reflection!

Total internal reflection (TIR) occurs when light strikes the surface at less than 60-degrees from vertical. From Snell’s Law, it will be refracted to less than 41 degrees from vertical and be reflected by the glass or acrylic back into the aquarium.

For light from a MH bulb to strike the water at less than 60-degrees from vertical, it must be at a height at least (greater than) half the horizontal distance to the glass. So if your tank is 16” from front to back, it needs to be greater than 4 inches high. Your suggestion of 6” to 10” is even better!

[hahnmeister]

Okay, just tried it... I cant see any of my T5s. With my eyes close to the water surface, close to the tank, the water surface at that angle looks black, and I cant see anything like a T5 or light source.

And while raising the halide might be great for lowering light loss (as a point source gets farther away, the cross section of light, or dispersion field, that the tank gets is less curved, and more linear), but it takes away from a halide's greatest advantage... those peak outputs that are only made available by being close to the bulb.

[hahnmeister]

okay, heres how Ill do it. here is a basic PFO halide reflector... very common, and similar to the SLS ReefOptics as well. Check out the angles of output...

http://i90.photobucket.com/albums/k278/wetworx101/PFOpendant.jpg

[hahnmeister]

Okay, I started doing the spec work, and then I realized it wasnt even necessary. Heres the diagram FWIW.
http://i90.photobucket.com/albums/k278/wetworx101/PFOpendantspecedout.jpg
Now, a parabolic T5 reflector is really the same thing.. multiple facets to angle the light downwards. Considering that most of the light, even with multiple smaller reflectors that have the same geometry, is coming out at an angle 45 degrees of less, that means that most of the light travelling in the tank will be at 33 degrees or less once underwater, and that is well beyond the necessary angle for the light to be lost no matter what the type of bulb.

[hahnmeister]

But with either setup, we cant claim that the water is going to be perpendicular to the light ray... ripples and waves prevent that, and even with a still surface, there is still some bit of reflected light from the water surface. With a halide, this means that the canopy gets illuminated. With T5s, this means that the light gets captured by the next reflector (or the one next to that, etc), and sent back down into the tank. The reflectors cover a larger area.... much the same reason why lumenarcs light up tanks so well. The thing is, with multiple smaller reflectors, you have a larger net area where the light is entering the water at a perpendicular to the surface. Look above at the green lines. I would consider the area between these lines to be the boundary for 'useful' light. At 8" of height, that only covers about a 12" wide area. A T5 setup would cover more than that, not to mention width. If you are not directly below the light source, you are getting light at an angle that makes it less intense... simple as that. Its alot like the surface of the water is a mirror, and we are trying to keep the light from escaping... so the best reflector is the one that covers the most area.

The proof is as easy as me taking PAR readings from the top of the tank... the light that is reflected upwards by the water. On my halides, just 8" above the water I can get readings as high as 180 PPF!!! I actually run a refugium in my canopy from all of the light that is reflected back up from the water into the hood. Most areas above the water with my 250wattDE PFO pendant are shining about 14-20 PPF back up at the ceiling. Thats alot of wasted light!!!

Taking PAR readings from above my T5 tank facing down, you can guess what the PAR readings are... 0... because any light that gets reflected up gets caught by another reflector and sent back down into the tank.

[hahnmeister]

Oh, and heres the proof about the 'wasted light' coming through the glass. Now, I have two 40Bs that have nearly identical light fields inside. One uses an 250wattDE EVC 20,000K. The other uses a 6x39wattT5 setup. The T5 setup has 2x aquablue, 2xblue+, and 2x actinic+. FWIW, the aquablues are at the very front and back, and the blue+ bulbs are the two in the center. The halide is about 6-7" above the water surface, and the T5s are about 4" when I take readings, normally only 2" though, but I need the clearance.

They have nearly identical spectral outputs, but the overall winner is the T5 setup. The real wattage of the T5s is about 240, and the halide, about 320! You can see the PAR ratings here:
http://i90.photobucket.com/albums/k278/wetworx101/40BMHPAR.jpg
http://i90.photobucket.com/albums/k278/wetworx101/40BT5PAR.jpg
They are nearly identical light fields in the two tanks. The halide does have a peak at the top center that is slightly higher, but due to its distance from the water, the 2000+ PAR wont actually reach inside the tank... its more like 600-700 at most. Now, while the T5s top out at about 500 PAR at the surface, its the entire surface, not just a 8"x12" square at the top like with the halide. The upper corners of the halide tank are downright dull in comparison. Now, at sand depth, the readings are very similar... 120-150 at the corners, 200 in the center.

Im really just trying to establish the fact that the two tanks are about as matched as you can ask for as far as comparing T5s to MH.

Okay, so I took the PAR sensor and held it against the glass... taking readings all over. I thought at first I would have to describe it with a graph/diagram, but as it turns out, the results were very consistent and any overlap in the readings needing further comparison wasnt needed.

The halide lit tank put out a PAR of 8-11 throughout most of its front glass surface. The T5 lit tank put out a PAR of 4-5. Now, this was with holding the sensor at a slight angle as well as perpendicular to the glass. On both tanks, I should note, the bottom few inches jumped up of course... to levels above 10, but this is due to the white sand reflecting the light and a different story.

[Navyblue]

Wow, I didn't expect that I can learn so much by asking here. Thanks all of you guys for the contribution. It seems that watt for watt MH and T5 aren't that different in par.

[mile sq. reefer]

150 MH / T5 combo. Your tanks is wide enough to use one these fixtures. Good amount of balanced light.

[Navyblue]

Wow, I didn't expect that I can learn so much by asking here. Thanks all of you guys for the contribution. It seems that watt for watt MH and T5 aren't that different in par.

[pjf]

Excellent experimental work, hahnmeister!
Light loss through the top of the aquarium is certainly stemmed by the large tube reflectors.

[cgarsmokr]

<a href=showthread.php?s=&postid=8813502#post8813502 target=_blank>Originally posted</a> by hahnmeister
Oh, and heres the proof about the 'wasted light' coming through the glass. Now, I have two 40Bs that have nearly identical light fields inside. One uses an 250wattDE EVC 20,000K. The other uses a 6x39wattT5 setup. The T5 setup has 2x aquablue, 2xblue+, and 2x actinic+. FWIW, the aquablues are at the very front and back, and the blue+ bulbs are the two in the center. The halide is about 6-7" above the water surface, and the T5s are about 4" when I take readings, normally only 2" though, but I need the clearance.

They have nearly identical spectral outputs, but the overall winner is the T5 setup. The real wattage of the T5s is about 240, and the halide, about 320! You can see the PAR ratings here:
http://i90.photobucket.com/albums/k278/wetworx101/40BMHPAR.jpg
http://i90.photobucket.com/albums/k278/wetworx101/40BT5PAR.jpg
They are nearly identical light fields in the two tanks. The halide does have a peak at the top center that is slightly higher, but due to its distance from the water, the 2000+ PAR wont actually reach inside the tank... its more like 600-700 at most. Now, while the T5s top out at about 500 PAR at the surface, its the entire surface, not just a 8"x12" square at the top like with the halide. The upper corners of the halide tank are downright dull in comparison. Now, at sand depth, the readings are very similar... 120-150 at the corners, 200 in the center.

Im really just trying to establish the fact that the two tanks are about as matched as you can ask for as far as comparing T5s to MH.

Okay, so I took the PAR sensor and held it against the glass... taking readings all over. I thought at first I would have to describe it with a graph/diagram, but as it turns out, the results were very consistent and any overlap in the readings needing further comparison wasnt needed.

The halide lit tank put out a PAR of 8-11 throughout most of its front glass surface. The T5 lit tank put out a PAR of 4-5. Now, this was with holding the sensor at a slight angle as well as perpendicular to the glass. On both tanks, I should note, the bottom few inches jumped up of course... to levels above 10, but this is due to the white sand reflecting the light and a different story.
huh? lol

[pjf]

Hahnmeister,

You have not accounted for three sources of T5 light loss in aquaria:
• Between the tank and the fixture. If you can see the tubes, that light is lost.
• Absorption by the tubes. Light that strikes the tubes are absorbed. Reflectors can direct upwelling light back into the tubes.
• Loss through the side aquarium glass from rays that strike the water at a shallow angle (more than 60 degrees from vertical). You can see part of your tubes by placing your eye against the side glass and looking upwards. If you can see the tube, that light is lost.

Currently available parabolic reflectors (i.e., Lumen Arcs) with MH point sources can avoid all of the above light loss, including the redirection of upwelling light.

[hahnmeister]

Sorry, but I dont see how a good T5 reflector would result in any more light loss than with your halide reflectors. FWIW, I thought I proved pretty well how T5s get more light into the tank than halides, and I dont seem to have these problems with my T5s that you talk about. I would imagine that there are better and worse reflectors for both T5s and halides that impact what you are talking about. Much of what you say for T5s as far as them being a disadvantage can be applied to halides as well.

[pjf]

Light loss from point sources of light such as metal halides can be minimized in three ways:

• Total Internal Reflection (TIR). Parabolic reflectors can direct reflected light downwards and ensure that light will strike the water within 60 degrees of vertical – critical for TIR.
http://reefcentral.com/gallery/data/500/93304Parabolic_Reflector.gif
In the reflector above, two-thirds of the light is reflected downwards and 1/3rd is dispersed in a 120 degree angle. The dotted line shows the 120 degree spread of direct light from the bulb at the focus of the parabolic reflector. This is the worst case or maximum spread of the light that will still result in TIR. By extending the skirt of the parabolic reflector, the spread will be less and still ensure TIR.

In contrast, tube lighting loses light that travels towards the ends of the aquarium because they strike the water at too shallow an angle for TIR. Egg crate louvers are often used to prevent this. If the louver is removed, then light from tubes will be seen refracted on the floor next to the ends of the aquarium.

• Upwelling light can be returned to the aquarium by large MH reflectors, such as Lumen Arcs. In the picture below, upwelling light is sent back down. If a T5 fixture is used, the reflectors will direct this upwelling light to a tube that will absorb it.
http://reefcentral.com/gallery/data/500/93304parabolic_reflector.GIF
• Minimal Light Absorption. At the focus of the parabolic reflector above is the MH bulb. Unlike a tube, it is too small a target to absorb the rays of light. A T5 will absorb the light that strikes it including the light returned by its reflector. Light emanating from a T5 heading directly upwards is reflected back and absorbed for an immediate loss.

• Minimal Loss through Air. The MH fixture can be adjusted in height so all of its light can strike the water. This height adjustment can be made and still allow several inches of air space between the lamp and the water. Using the first illustration, simply ensure that the dotted lines meet the water at the edges of the tank. In contrast, fluorescent light often misses the water and can be readily seen by an observer if no hood or louver is available. If you can see the light source, that light has missed the water and is lost to the aquarium.

[hahnmeister]

These seem like relative comparisons to me. Any reflector for a T5 or halide can have those characteristics. The geometry of good T5 reflectors prevents much of what you are talking about though.

"If a T5 fixture is used, the reflectors will direct this upwelling light to a tube that will absorb it."

Yeah, and the light that gets reflected from a halide ends up illuminating the canopy or your ceiling.

Sorry, but beyond the halide taking up less space, and the T5 tube being longer, I dont see how one reflector would be better than the other. If you want a T5 reflector that behaves as well as a halide, you can. Personally, I find the idea that you can mount your T5s that much closer to the water surface to be a much larger advantage than halide. Even if what you are suggesting is true, the PAR numbers given support T5s linear distribution to be a better type of light than the point-source halide.

[pjf]

I think that current MH and tube lighting are both adequate for generating PAR for aquaria. Some of the issues that we see now involve too much light. Dana Riddle has found that even 100 PAR induces photo-protection in some SPS corals. Until some future researcher discovers that dynamic photo inhibition is beneficial, all of the major lighting methods, MH, T5 and LED, are adequate. In fact, this issue of dynamic photo inhibition and its benefits will better determine the direction that aquarium lighting takes than the specific issues of reflectors, TIR and light loss.

I’m frankly looking forward to LED lighting. The promise of lights without ballasts and with an easily controlled resistive output is very appealing. The Grim Reefer predicts that they will become modular, so we will be able mix and match spectra just as you mix and match T5 lamps for optimal results. I wouldn’t mind checking back with you at a later date to see what innovative means you have devised to employ the new lighting.

Thanks for being a compleat aquarist. While I may not agree with every little tittle you say, your writings are certainly insightful and causes one to look at issues from different perspectives. I’ve enjoyed reading your posts and have learned more from you than from all of the aquarium textbooks that I’ve read.

Have a Merry Christmas and a Happy New Year!

[hahnmeister]

Yeah, I predicted that LEDs will become modular as well... it just makes the most sense since bulb-husbandry will become a new challenge with LED's. Their narrow output, and near polarized, almost monochromatic laser-like beam of light will present its own set of challenges. I cant see them being very useful without interchangable lenses and colors, since you can get a red that is just red, a green that is just green, and a 420nm that is just 420nm. Everyones tank will have to have their own, customizable LED system depending on the tank's dimensions (do I want a narrow output for a tall narrow tank, or a wide one for a shallow grow-out vat?), and do I want 9 blue LED's, or just actinics? It will be more complicated than T5s.

My LED's are not as problematic, yet. Im using 5mm LEDs in pre-made spotlights... sucks up less time. FWIW, the better LED systems will have some sort of ballast though. Some sort of controller is needed for sustained output, but I agree with you that at least it wont be a huge core&coil like a halide.

Merry Christmas