What is the difference?

[reefhead]

My LFS had a frag of Green M.Digita setting in a bowl on the bottom of there 180g lite by 3 400w 6500k 14" above the surface.

After I took it home and placed it 6" from my 175w 10k it has basicly lost all color.This also happened to another piece of the same species a few mo. ago.My purple tip acro is growing with great colors.

What is the difference in par/spec? and, is that the cause?

[Bruce]

Reefhead,

There is a phenominal difference in the PAR found in one 400 watt 6.5k compared to the par found in a 175 watt 10k. I believe a 4 fold difference is accurate. I dont have the actual numbers on the PPFD of each bulb, but if you search this forum for Sanjays Spectral Analysis of MH bulbs, the info there speaks for itself.

Now, compound this difference in PAR between one 175 watt 10k, and one 400 watt 6.5k, then remember there were 3 400 watt bulbs over this coral originally. The coral went from extremely intense lighting, to moderate lighting. Give it some time though, as its color may return. As long as it isn't bleaching give it a chance.

I am sure someone will be able to post the link to the Spectral Analysis page that was posted on this board several months ago.

[reefhead]

can anyone else contribute

[Ironreef]

That was the difference. extreme light to modest lighting. 400w Iwaski is the most powerful. 175w don't pack much punch. even if it was 400w 10k you just can't compare with 175w. The purple tip did it come form simular lighting.? I belive it would be the same if it came from 400w

[reefhead]

may point was that the frag was at the bottom of a 180g Tank with the 400w bulb still 14" above the water.

Now, what is the difference in par travling to the distance

[reefhead]

SHOOT!


I need a move to lighting!![img]/ubb/biggrin.gif[/img]:

[Ninong]

OK, I'll move this to the Lighting forum for you. The PPFD (PAR) of a 400w 6500K Iwasaki is 199.7 on an MV ballast (the type recommended by Iwasaki Corp.). The PPFD of a 175w 10,000K Ushio is 63.41 on a magnetic ballast. I have no idea what the actual figures would work out to based on the different distances you are asking about.

There are also significant differences in spectral analysis between these two lamps. The Iwasaki has considerably more energy in the yellow-green band than the Ushio 10K. People who have used both 6500K Iwasakis and 10,000K Ushios report differences in coloration on certain SPS corals.

Ninong [img]/ubb/smile.gif[/img]



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Irrational Exuberance!

[reefhead]

the purple tip Ive had for 2 years, its probably just adapted.

I just cant figure that the Digita would have this much loss of color.The frag again, was sitting on the bottom of a 180 with 400w lights way above.(14" above water surface in bell pendents

Thanks gang!

joe

[andy-hipkiss]

Hi,

Much depends on how deep the original tank was and what type of reflectors are being used. However, judging by the figures I get from my tank (2x400W Ushios, and measured using an Apogee PAR sensor) then the frags probably had around 300-400 uE/m2/s if the tank is 24" deep. Your 175W at 6" (is that the total?) would be around 600-800 uE/m2/s.

IOW you've just severly INCREASED the PAR falling on the frag ...

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Cheers
Andy
http://www.andy-hipkiss.co.uk

[Ninong]

Hi Andy, welcome to Reefland! [img]/ubb/biggrin.gif[/img]

IMO the Apogee PAR sensor could be useful to compare readings at different depths of the same light source. You might be able to take readings of a 400w 10,000K Ushio/BLV lamp at 10" below the surface and compare that to readings taken at 15" below the surface. I don't think it is a useful tool for comparing a 10,000K Ushio/BLV lamp vs. a 6500K Iwasaki lamp at all because the Apogee PAR sensor is seriously flawed. It underestimates light in the range 400-500nm (blue light) and overestimates light in the range 550-650nm (yellow and orange light). It cuts off completely at 650nm, giving no reading whatsoever of PAR from 650-700nm. The action spectrum of zooxanthellae peaks at 440nm and 670nm, yet the Apogee sensor gets no readings at all between 650-700nm.

The 6500K Iwasaki lamp and the 10,000K Ushio/BLV lamp do not have the same spectral spread and the Apogee PAR sensor does not accurately read the wavelengths in each band. It does pick up the central part of the band reasonably well, which makes it useful for studies involving terrestrial plants.

You need a very expensive spectroradiometer to accurately measure PAR. That's why the reading from an Apogee PAR sensor will not agree with the figures published by Sanjay Joshi in his tests.

Regards,

Ninong [img]/ubb/biggrin.gif[/img]

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"First, we would not accept a treaty that would not have been ratified, nor a treaty that I thought made sense for the country."— George W. Bush, On the Kyoto accord in an interview with the Washington Post, April 24, 2001

[andy-hipkiss]

Thanks Ninong nice to be here,

I think you are overstating the weaknesses of the Apogee, that aside, its worth reviewing what you said ... "It seriously under reports the shorter wavelengths", true yet my readings is far greater that Joshi/Morgan's. Therefore, I believe my comments are still correct. I was not trying to compare the 6500 vs the 10000 (I only have figures for the BLVs) beyond saying my "understated" figures are (much) higher than J/M's 'accurate' (LiCor) reading ... interesting huh?

As I said, I've no idea whether this is due to variations in the ballasts/mains supply, but the high on yellow Iwasaki appear to be not the dominant force that was previously thought espcecially when one also factors in a PUR curve.

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Cheers
Andy
http://www.andy-hipkiss.co.uk

[Ninong]

What's the code for a wink?

The same as for a regular smilie except use a semi-colon instead of a colon. [img]/ubb/wink.gif[/img]

Ninong [img]/ubb/biggrin.gif[/img]

P.S. - When you have the reply box open, just click on Smilies Legend to the left.


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"First, we would not accept a treaty that would not have been ratified, nor a treaty that I thought made sense for the country."— George W. Bush, On the Kyoto accord in an interview with the Washington Post, April 24, 2001

[reefhead]

Originally posted by andy-hipkiss:
Your 175W at 6" (is that the total?)

IOW you've just severly INCREASED the PAR falling on the frag ...

Yes, that is the total.

there 400w 65k are in a bell pendent designed for industrial use.The bulbs were 14" above the water and the frag was in a AGA 180 at the bottom.(pretty far away from the light)

As of this post the frag is dead,Its got me wondering(everything else is doin great!)[water params are fine]

Thanks, joe

*Welcome to Reefland.Com Andy!

[andy-hipkiss]

Joe,

Leaving aside the esoteric debate about Iwasaki's vs BLV's and my questioning some of the current interpretations of the figures ....

Bell pendants aren't the greatest so in ballpark figures and talking in relative terms ... you have doubled or tripled the PAR hitting that frag. It can be done but not always sucessfully (as you found out).

I know the purist will say the Apogee isn't as good as the LiCor ... but for $89 (assuming you have a multimeter) it will give you a reasonably good handle on what the frag came from and where you are putting it. Let's really overstate the issue and say there is 50% error when comparing a 6500K, a 10KK and a Radium (all bets are off with the 12KK as I've never seen one [img]/ubb/smile.gif[/img] ). A 50% difference will probably be handled fine, A 300% one not. That's the thing I hate about light and its inverse square law ... tiny differences in depth make a huge difference and can easily swamp the commen-sense conclusion that a 175W isn't ever going to produce more light than a 400W.

Thanks for the welcome ... great forum. Its been a while since I've had to get my Kirk Photosynthesis book out ... not sure that is a good thing though ;-)
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Cheers
Andy
http://www.andy-hipkiss.co.uk

Editted: What's the code for a wink?

[This message has been edited by andy-hipkiss (edited 05-27-2001).]