Interesting Articles On Lighting And Coral Colouration

[Crazy fishes]

I have had sitting in my favourites list a few links that I found some time ago; never had the time to read them properly. It is a little more in depth than the usual information and literature like reefkeeping magazine online that we commonly read but is very good and clears up some common misconceptions while creating new questions. I hope you can benefit from these articles and have a look around at past issues as it contains a lot of valuable information.

http/www.advancedaquarist.com/2007/3/aaf...arget%20feeding
http/www.advancedaquarist.com/2005/12/aafeature2/view
The first is a feature article: How Much Light?! Analyses of Selected Shallow Water Invertebrates' Light Requirements and the second is a feature article: Colors by the Thousands - Light, Colors and Corals, Part I

Happy reading

Regards

 

[xxBarneyxx]

Only read the first article but it is really very interesting! Thanks a lot for posting the links.

I dont know enough to be able to poke holes in it but it seems fairly clear. The only thing I would have liked to have seen is the same tests done in 24" of water as well as 12" (a fair portion of marine tanks are around 2ft deep so it would be interesting to see what effect the extra foot has on the PAR). That is really something that is another discussion though and Im sure that has been tested many times.

However they start by kind of implying that 400w MH are overkill, looking at the results it seems that you would probably need 200w MH for the 12" depth to reach the saturation points so depending on how that extra foot of water effects the PAR you might well be needed the 400w MH to be hitting this? (I could of course be completely wrong, I dont know enough about lighting to discuss it intelligently for too long ).

 

[SkiFletch]

Nice articles CF. A lot of research has shown recently that ~200PAR is a common saturation point for corals and that going above that is overkill. Good to see some more articles confirming that. Of course this varies with the zooxanthellae in the coral's tissue, but it's a good number to shoot for. I can comment about the depth thing with halides.

My own setup is a 2x175watt halide (no actinics, etc) just under the surface my PAR ranges from 250 far from the bulb to 350 near the center of the bulb. At about 1' down it ranges from 150 to 200 PAR. And at the bottom 2' down I get ~90 to 125 PAR in any places not shaded by rockwork. Gives you an idea of the effect of depth on PAR. So down on the sand I'm nowhere near the saturation point for most corals, and as such I try to keep my deeper water corals or those that I can suppliment with feedings down there. The only exception is my elegance which is a shallower water species that I keep deep in my tank out of necessity. It still does very well though cause my clowns feed it all the time.

Anyway, with 175watt halides, I wouldn't go deeper than 2' and even there, they're not great performers. 250watt halides do a much better job on 2' deep tanks and as Barney assumes, most 400watt setups are overkill on 2' deep tanks. Some guys in my club running 400's are getting like 700PAR shallow and 400PAR on the sand.

 

[kj23502]

omg, this is some really deep stuff. I read it and searched for watt values (or ratios) to lux, lumen and such and found this:

http/www.fishkeeping.co.uk/articles_28/l...ur-aquarium.htm

It talks about keep freshwater plants but I assume that some things are still similar. I dunno...trying to figure this crap out.

 

[SkiFletch]

Lux and Lumens are great measures when considering planted tanks as most freshwater plants have multiple carotenoids within their chloroplasts and can use many different wavelengths of light. Therefore measuring light of the visible spectrum (lumens) and comparing it to surface area (lux) is a great way to predict success wtih lights.

Living in deeper water, the carotenoids within the chloroplasts of the symbiotic algaes that our corals derive their energy from are SIGNIFICANTLY more limited. Usually only one or two wavelengths are used by our corals whereas freshwater plants may have 2-5 times as many options to use. Because our corals are limited, using a measure like PAR (photosynthetically available (or active) radiation) is really the way to go. PAR really only looks at available blue, purple, and red light. It ignores green, yellow, and orange light that our corals haven't a prayer of using anyway and thus is a much better predictor of how good a specific ballast/bulb/reflector combination may be.

Lumens and Lux do however provide a good starting point for considering if a lighting option is even worth looking into. Cause if a light's rating in lumens is low, no matter how perfect it's color spectrum it won't be worth anything anyway