Spectrum and Photosynthesis

[blide]

Found this statement in Reefkeeping this month, so I've been reading a lot about "kelvin" and was wondering if you guys could help me out some. I have three different MH bulbs at home XM10K, Hamilton 14K, and XM20K. So naturally I want to use the best looking and best bulb that promotes photosynthesis .

Most have seen my 20g nano setup and it's basically one 250w MH w/ no actinics. I'm really interested and promoting photosynthesis and was wondering if it would actually make a difference on this little tank if I used one of my different kelvin bulbs due to there being so much wattage of light on a small tank.

Plus can anyone explain this graph I got off of Sanjay's site? I know there's different peaks, but to me the XM20K looks like it covers the whole spectrum with added peaks that the HM14K doesn't...

 

[psteeleb]

visable wavelenght is from 400-700nm
the lower the number the more blue, the higher more red

as you can see in your chart there is a spikes way over toward the 400 or blues for the 20k with little coverage over the total spectrum

the 14k bulb has more light intensity over the spectrum and should be better for coral growth. granted the spike is not as high in the blue, hence not as blue a light but it is in the blue range that gives it a 14k rating

here is another chart that may help show what I mean

 

[blide]

That's the thing I know both bulbs cover the full spectrum just not as equally intense (fairly close though), but since I'm using a high wattage bulb over such a small tank I thought that might give the 20K the advantage buy offering a more actinic option which from what I have read aids in photosynthesis. :?

 

[psteeleb]

I agree witht the size per gallons perspective but still feel strongly that the 14k will give much better growth. Other then the one value in the 545 range the 14k has 2 to 3 times the intensity in the spectrums that mater for growth.

 

[Guest]

i think it also depends on the corals too some are harvested in shallows while others deeper waters....so some will respond better to 20k for deeper water and 10k for shallow water.

i also believe ballasts make a big difference i get different coloring using the same bulb. i just changed from pfo ballast to coralvue ballast... this my .02 not and not a light expert

good question to ask sanjay at next wave....free plug

 

[kwl1763]

Lots and lots to explain here?

phtosynthsis occurs over a spectrum that is very wide but can be very short for specific things.

Corals have zooxanthellae that don't have flat spectral requirements. There is even some evidence of bluer spectrunm helping proteins and slightly increasing photosynthesis but not a ton. This is one of the best articles about it I've read!

http://www.advancedaquarist.com/2002/2/aafeature/view


Bottom line is go for the highest PAR you can stand to look at. So in that case the 14k would be a better choice in my opinion.

http://www.dynamicecomorphology.com/publishoceanslideseries.htm

This is also a pretty good CD to learn more!

 

[Rick]

In most cases the bulb with the lower kelvin, closer to sunlight has the most PAR and thus corals grow the most. The bulb that is known for the fastest growth is the Iwasaki 65K. The problem you may have on such a small tank is with too much PAR. Corals can get too much PAR in our tanks and actually stunt them and even put them in decline.
Because as a coral is photosynthesizing there is respiration. The more PAR the more photosynthesis, the faster the respiration. It can only get to a certain point where anymore light will cause the coral to decline. Much like us running till we were out of breath and then sticking your head in a bag.
That is where flow comes in. The more flow around and past the coral, the more fresh water it gets, the more oxygen it can get. The flowing water takes away the Co2 produced and brings more fresh oxygen for the coral to continue this high respiration.
In my tank I have a huge acro colony right below the water under a 400 watt light. It is really healthy and grows fast. But if I removed the wavebox and the 4 Tunze streams in the tank and just had the two return nozzles for water flow, the coral would most likely go down hill fast.

 

[blide]

Hmm, that gives me an idea what if you covered the full spectrum from top to bottom. For example if I have a 10K and 20K running seperatly at equally 250w, but producing different PAR levels. So, if I ran one 20K MH morning and afternoon/evening and one 10K mid day the PAR would be higher and the somewhat full spectrum would be covered right? If so then the only thing you would really need to know is how long of a photo period for each bulb...

Here's Sanjays bulb comparison...

 

[kwl1763]

Lets simply. Basically corals care about PAR. what few studies have been done have suggested thye could care less about the spectrum (within reason) so corals care about PAR.

Basically corals need different levels of light. with acros generally being fine with pars well over 100 and some softies being fine in the 20s.

It's very difficult for us to get sufficient levels of light to the bottoms of our tank to grow acros. You need at least 200 par above surface to get 100 below. So generally us SPS freaks try to have a lot of PAR so we can grow our acros all over our tank.

However, if you're willing to do a little planning you can have a lower PAR bulb and still be fine. But don't expect to run that XM 20k 10 inches off the water and put an acro on the bottom and off to the side and expect it to do well!


So my advice be less worried about the spectrum and getting coverage there and more worried about the par values. Rick is right if I could stand it I would run Iwasaki 6.5k but they are horribly yellow and immposible to look at! 20ks look great but the PAR is generally pretty bad on them. So I've settled in the 10k range as it's a good compromise for my SPS tank. You may decide you really want 20ks. They will work fine, just put your SPS high in the tank and under them!

I never could get over the waste of the 20k bulbs personally! For the same electricity I'm getting half the light output with the 20k. It' s a bad tradeoff fo rlooks in my opinion.

 

[blide]

@kwl1763 wrote:

I'm not really worried about the PAR hitting the bottom of the tank (it's only a 20g) and I understand where you coming from, but I'm just trying to comprehend some of the "Kelvin" stuff making a difference in photosynthesis. Here's a pic so you know what I'm dealing with...

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[kwl1763]

@blide wrote:

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Short answer, it doesn't make much if any difference. Read the AA article above!

 

[blide]

@kwl1763 wrote:

Short answer, it doesn't make much if any difference. Read the AA article above!"]"]

Hehe, I did and it contradicts this month Reefkeeping article and the AA is from 2002.

AA -"This experiment's results suggest information potentially valuable for hobbyists - that rates of photosynthesis were essentially the same under these two distinctly different light sources. Other than aesthetic value, there appears to be no advantage, photosynthetically speaking, in using high Kelvin lamps."

RK - "They produced light in the area of 420-450 nm, and that happens to be a wavelength relished by photosynthetic algae. "

Not saying is wrong just trying to collect as much information possible...

 

[Ashlar]

Such is the state of our hobby and what we know. 75% anecdotal observation, 20% books and magazines, and 5% scientific research that either is targeted at or can be applied to aquariums.

Looks like the range of photosynthesis is 6-14kK, with a sweet spot between 420-450nm. The XM 10k seems to be closer to that sweet spot, and overall has more PAR.