<a href=showthread.php?s=&postid=13421831#post13421831 target=_blank>Originally posted</a> by onetrickpony
For a 48" X 30" tank what do you think would work out better, greater light penetration?
The Lumenarc III with a wider spread and higher PPFD
Giesemann 400W Coral with PFO 400W HQI PPFD 209 with 1 Lumenarc III
Or
The more focused Lumenbright with lower PPFD
Giesemann 250W Coral with PFO 250W HQI PPFD 126 with or 2 Lumenbright
Thanks
Ken
Something to consider:
Ive reminded Sanjay every time I see him that something is wrong with the Giesemann 14,500K/Coral bulb (the 13,000K is the 'Marine' bulb) in the charts. The bottom chart is if you compare 'unsheilded' to 'sheilded'... notice how the 'sheilded' is higher than w/o? If anything, these should be reversed. I think he mentioned that he was going to redo these bulbs all together.
Here is another tidbit... the Giesemann 14,500K 'Coral' is really a Ushio Aqualite 14,000K, which is the same as the BLV nepturion 14,000K. There may be some 'bin picking' or something, but lets just say Giesemann doesnt make their own bulbs.
Now, if you look at the BLV nepturion 250wattDE 14,000K (which within Ushio they will openly admit they are the same bulb, Ushio is the brand for the US, and BLV has Europe... thats all), it comes in at 85... same as a pheonix. The weird thing is, when I take readings on the Ushio 14,000K vs. the Pheonix 14,000K, the Ushio is a good percentage brighter... perhaps 20% more than the the original... I would say enough to make the Ushio/BLV more like 100 than 85. Once again... bulbs vary from batch to batch which could easily explain some of this... you never know if you got a 'dud' unless you test it. I have a friend who is running 6 Ushio 14,000Ks at any given time, and for some reason, one of these bulbs has come in a good 25% lower in output from day one through one year... you couldn't tell unless you use a meter, but its there... just a 'bad batch' most likely... just like auto motors... you think your car has the '200hp' as advertised? Truth is, it could be 180, or even 220hp. Stock Dodge Vipers that were supposed to get 450hp used to vary from 420hp to almost 600hp right off the line! This is just variation on the assembly line.
If you look at the 400's... the Giesemann 14,500K/Coral and BLV 14,000K are easily the same bulb.
So something to consider... FOR SURE, the Giesemann 14,500K Coral does not have a PPFD of 126 w/ sheild. I could see 101 though because thats similar to what I see with the Ushio. Also, the 'Coral' is not a 13,000K, but Sanjay has mentioned that is how they were sent to him from Giesemann... so whatcha-gonna do?
Now, according to Ushio, the PAR/watt ratio of the 250wattDE 10,000K is 56, and the ratio for the 14,000K is 56... which makes them the same... and if you compare Sanjay's results... you will see that besides some minor spectrum changes (which in person do make a huge difference), the bulbs are similar in PPFD. Now, Ushio puts the 10,000K 400 watter's PAR/watt ratio at 95! The weird thing is that Ushio's 10,000K at 400 watts has a lower output than the BLV 14,000K (which has a nearly identical output to the G-man Coral 400)... so deriving a 'PAR/watt' ratio for the 14,000K 400watter is ??? (Ushio doesn't have it listed in their info, just the 10,000K at 400 watts... go figure)... but from all the other bulbs, it is safe to say that as you go from 250 watts to 400 watts, there is a significant increase in efficiency.
On the other hand, having only one light source for a tank tends to make all of its corals grow with a phototripic effect... the tips are all aimed at the light, many more shadows are cast so pigmentation on many SPS corals is faded over more of the surface. A lumenarc might make the light source 'not as much of a point source', but it still is to a large extent. All you have to do is look at the grid testing Sanjay has done to see that the light still loses intensity as you move away from the bulb in height as well as side to side. Consider this... a reflector, even a 'great one' like a lumenarc which attempts to spread out the point source of a bulb (to minimize the effects of the inverse square law), is really only dealing with the light that is coming out of the back 180-240 degrees. Most of the light that is coming from the front half of the bulb never touches the reflector, and so is still a 'point source'. The light that does come from the reflector still loses about 5% of its intensity right off the bat due to the material, and no reflector is perfect (unless its an LED) so you lose some more light that hits the reflector more than once, or hits the reflector right above the bulb and is aimed right back at it (why the backside of a lumenarc style reflector is just flat, Ill never know... a small dimple/cone there makes more sense... or at least a 'V' groove restrike like a spider light reflector). The light that comes from a reflector also has to travel FROM the bulb to the reflector, being subject to the inverse square law on the way, and then be redirected downwards as best as possible... the larger the reflector, the greater the dispersion... the greater the intensity is maintained with distance from the reflector... but a larger reflector means the light has to travel more on the way to the reflector in the first place...
Bottom line: even with a very nice reflector like a lumenarc 3 full size... you still have phototropism. So if you have two reflectors running 1/2 the output, you are still ahead of running one reflector with all of the output. You will prevent phototropism, you will maintain intensity with depth better, etc. But when you switch from 250's to 400's... you are talking about increased efficiency as well (HQI 400's is something around 540 watts with the bulbs were talking about!, and a HQI 250 is going to be about 330 watts... or 660 watts combined). So there is no clear response on this... the cost of bulbs, ballasts, and reflectors is more with the dual 250's, and the efficiency isnt as great, but it might be better for you in the long run still because of the 'spread' of light that it gives you.
I have dealt with people who light larger tanks with one large bulb... like 48x48x24 tanks with a single 1000 watt bulb (1000's have great efficiency, but then again, you are talking about mounting the light a good 24" or more above the tank, and how much light are you spilling into the room then?), and the owners didn't like it. The corals had their pigmented tips all facing the center of the tank (away from the viewer), lots of shadows (LPS,softies, brains, etc. like it, but not SPS so much).
I have lit 40B's with single 250 watt halides, and I didnt like it much in the end either because of this phototropic effect. On my own 48x30x21"h reef, I started with a single 250wattDE (Ushio 14,000K) on a light rail (rather than two halides that size) moving back and forth about 24" in the center, with 4x54watt T5s for supplimental blue and actinic. In the end, more due to pigmentation reasons (not even this matched the intense colors I get with 100% T5s... the growth otherwise from the light mover, which prevents phototropism the best of anything, was awesome), I went 100% T5.... 10x54wattT5s (tank is eurobraced so I only have a 24" opening good for about 10 T5 bulbs). You might consider the same as yet another option. I thought the 50/50 halide & T5 combo might be the best from both worlds, but I suppose not in the end... 540 watts of T5s (about 625 watts at the outlet) provides about the same intensity, but the spread makes the corals pigment in all over their surface. It seems that if having to pick between a focused more intense light, and a light that is say, 30% less concentrated, but more 'diffused' (coming from more angles), SPS will go with the more diffused light. LPS, OTOH, have a harder time with this, so the tank either needs to be taller to compensate, or the corals need to be kept under/close to an overhang so they aren't getting light from every angle. If you like the 'deep blue sea' look more than a daylight look, T5s are better at making the 'blues' anyways.
I dont know what height your tank is, but with my lights, I wish I would have made the tank a little taller now... like 24"... so you should be covered. I also never used the highest output bulbs... lots of actinics and misc 'test bulbs' (to break them in for spectrometer testing), so my 10 bulbs were never nearly as powerful as they could be. If you like the more 'daylight' or 'day/blue' look (what you get when you use 10,000Ks and lots of blue T5's), you could use more daylight/6500K lamps, less actinics (plenty of blue+ bulbs though), and really scorch that tank from top to bottom.
