BigAl's slow chronicle . . .

[KodiakBear]

In theory, you could have two bulbs with very different K values with matching PAR. Most often you won't find that to be true when looking on the store shelves. The lower K bulbs are heavier in the red spectrum which benefits chlorophyll a much more than chlorophyll b (which is what is prevalent in most corals' symbiotic algae). The reason there is more growth in some lower K bulbs (15K vs 20K) would be that chlorophyll b will still absorb some of that red energy. The key is to try to find the balance between benefiting the coral and benefiting the nuisance algaes.
Here's a graph to show absorption of the two types of chlorophyll. The graph comes from an orchid grower's site, but I don't remember the link.

[BigAl07]

Ok this evening when I came home from a service call I got a VERY nice surprise... the sand sifting starfish was showing off on the glass. I snapped some quick photos....

[Dentoid]

psych!

[cracker]

NICE pic!

[Craig Manoukian]

Great pics Al!

[deaclauderdale]

Great shots Al.

[goldenmean]

now those are some awesome pics!

[BigAl07]

Thanks for looking gang I just got lucky with the pics

[Doot77]

Very nice pics of your star, the first time I saw mine on the glass I was very surprised to say the least.

[caitrina]

Cool pics. That is so neat when they do that and better yet when they do it and we are able to get pictures. OMG, imagine that happening before digital cameras...crap, no film, gotta run to the store to get film, come home...awww man, I missed it.

Everything is looking GREAT!

[BigAl07]

Thanks cat!! yeah it was a pleasure to capture it!!

[mps9506]

Originally Posted by BigAl07

Thanks for the input! So what's the "drawback" to higher "K" light as far as coral growth then? It seems many people have noted that Higher "K" bulbs may not provide as much coral growth as lower "K" but maybe they aren't comparing apples to apples in that sense. Can you have bulbs of various "K" rating with similar PAR?

Yes, you can have two bulbs with the same K but different par. They are not really related.
As a rule of thumb higher kelvin bulbs have lower PAR. If you look at the spectral plots of it becomes pretty obvious.
Why do we look at the color temperature of the bulb then? Well, it gives us an idea of what it will look like in the tank rather quickly. If you really want to know how your corals will grow under a bulb you need to look at the spectral plots. You need to know what wavelengths the peaks are at and how much energy there is at the wavelengths.
Kodiak's post above is excellent and right on.

I dunno if you have seen this page Al, but Sanjay Joshi has been writing about and testing for a long time. Sometimes it can be hard to understand, but you will understand it really well soon. It's basicly physics with a little biology and chemistry mixed in
Sanjay's Reef Lighting Info Pages
Plots of lots of bulb and ballast configurations. If you are really interested in coral growth and coloration that is what is important, not the K.

[BigAl07]

Thanks Mike. Yeah I've looked over those a couple of times. I have to admit it makes more sense now than ever and I am starting (just barely) to get my tiny teenie lil mind around this. Just so MANY variables involved! It's really hard to make a decision!!!

[tbittner]

Oh man, I hear you there Al. My tiny, teenie brain has trouble with simple math! And that post that Jack had posted with all the formulas... My ears still have smoke coming out of them...

Thanks for the link, Mike. Sanjay does an excellent job in explaining lighting and the effects it has on our confined reefs.

[BigAl07]

Originally Posted by tbittner

...... My ears still have smoke coming out of them...

Ditto bro! I afree 100% But little by little some of it's sinking in. Maybe in the next month or so I'll be "ready" to make a bulb decision. Hopefully