ichthyoid;399551 wrote: Rick-
Barry makes a couple of good points...especially the one about 'not taking his word, as he has only been at this 10 months'...
...I will borrow from that wisdom by qualifying my statements the same way. I have been in the hobby 35 years, am an engineer and well versed in optics, lighting sources, design, yada yada yada... so don't take my word for it either. What I offer here is an informed opinion, at best.
What matters in this hobby, is what works. Anyone that has been in it for any length of time has been humbled, sometimes in spite of their experience, etc. So I encourage you to learn, as much as you can, and have a lot of fun doing so. That being said-
Most of our corals, the photosynthetic ones, contain symbiotic dinoflagellates (also called zooxanthellae) which also happen to contain algae. The zooxanthellae are very small animals that got captured by the corals, and are held prisoner for the purpose of providing food to the coral. The algae within them absorb light and ammonia, and in the process produce sugars which feed both the zooxanthellae and the coral. All that matters to them, is that they get enough of the right kind of light and nutrients, in an environment that is acceptable to them (ie- they can handle chemically and physically).
The link that 'Oldschool' referred you to is, in my opinion, the most comprehensive and balanced single source on reef lighting that I have read on the internet. http://www.americanaquariumproducts.com/Aquarium_Lighting.html">http://www.americanaquariumproducts.com/Aquarium_Lighting.html</a>
It does go into a great deal of detail, and for some that may be a little too much. However, if you want to really understand this stuff, it's all right there.
A few things to consider:
1) all that the coral/zooxanthellae/symbiotic algae really care about is how much of the correct wavelengths of light actually get to them. This is where Photosynthetically Active Radiation (PAR) comes in. PAR is a very good indicator that the spectrum and intensity are sufficient, though not perfect (I will not go into that here for brevity). Without a PAR meter, some use watts, watts per gallon, or other rules of thumb to guide them in selecting lights. Please remember also, that once an organism has adapted to a certain light spectrum and/or intensity, it generally will get upset if you abruptly change those conditions (ie-going from old bulbs to all new bulbs, or a new light system). Change bulbs individually, rather than all at once. Change things gradually!
2) a 'little' science...much less light is needed when the reflector/canopy is designed correctly. As you look at others tanks, notice how much light spills into the room/on the floor/walls, etc. That light does not grow coral! What we want is a canopy/reflector that 'focuses' the light on the bottom of the tank. Light intensity, or 'irradiance' as it is known (watts per square meter), conforms to the "inverse square law".
What does that mean?
Double the distance from light to object (coral), irradiance is 1/2;
Double it again, it is 1/4th;
...then 1/16,
...then 1/32, etc.
This is huge!
3) we all got into this hobby for different reasons, but chiefly among them I will wager it is due to the sheer beauty of the creatures we maintain. I want the light spectrum and resulting colors, to be pleasing to ME. Please keep this in mind when choosing your light sources/bulbs. I really like 6500k bulbs. It gives a good balance of colors, and is able to reproduce reds and oranges much better than 10k-20k bulbs. This is not just my opinion, but backed up by a lot of research as well. Reds and oranges are common in marine organisms, in part because these colors absorb blue and green light (I will not go into that here either). 6500k also, generally, gives the fastest growth rates. I do suppliment with actinic bulbs. In practice this means that the 'spectrum' I am using is no longer purely 6500k, but is 'blue shifted' by the actinic bulbs. I have provided a good source of Red-Orange-Yellow spectrum though, in the process.
Also to consider-
The human eye is most sensitive to green and then decreases as the spectrum shifts toward both the red portion and the blue portion of the light spectrum. The response 'curve' of the human eye looks like a typical bell shape with the peak in the green, falling off toward the reds and blues. Photosynthetic pigments are almost the exact opposite of this. They are least sensitive to green and peak in the blue and red portions.
What does that mean?
By selecting light sources rich in blues-greens and orange-reds you will 'kill two birds with one stone'. You provide the wavelengths that both your eye is least sensitive to (ie-they need), and that the photosynthetic pigments require as well. Good looking colors, with good growth! Win-win! Woo-hoo!!! Life does not offer too many of those. Can it get any better?
4) Evaluate the Color Rendering Index (CRI) rating of each light source you are considering. This is in essence, a color reproduction accuracy rating. CRI of 100 means the bulb reproduces colors the same as a natural or 'full spectrum' light source would (an oversimplification). Your corals will not give a flip about this, but your eyes will. Please refer to #3 above for further consideration.
5) opinions are many, and guarantees are few. As my Doctor told me once ..."this ain't Midas Muffler. There are no guarantees." We all stand on the shoulders of giants here. The 3 secrets to this hobby are to 1) learn 2) learn and 3) learn. Everyone in the hobby has something to share from their experiences. Just be careful in evaluating whether information is valid and/or if it applies to your situation. This applies to 'laypersons' as well as 'experts' and books.
My 2.5 cents, hope this helps...
happy reefing![/QUOTE]
Well Done!
