Reef Tank Lighting... like science and stuff

[pdxmonkeyboy]

I was talking to someone at the meeting about lighting and pulled up this advanced aquarist article about actual light spectrum in the ocean and the difference between daily light interval numbers in the world and in reef tanks.   I am soo sorry, but i forgot your name, so PLEASE remind me.  Anyways, it is a really good article so I thought I would share, it kind of shattered my belief that most of the light underwater is blue, it is not, by a large margin the water is mostly green light. 

If you are serious about growing corals or understanding more about your lighting then A. realize that you need a par meter.  B. understand that you need to be concerned about the VOLUME of light you are giving your corals, not the INTENSITY.  It is a fact that evades many of us but it is actually quite simple.  God, I just realized this could turn into a huge post.  Anyways, this index of light is called the daily light interval or DLI. It is a simple calculation of intensity X time.   The DLI is critical in understanding that corals can only process X amount of light, after which time they shut down. This shutting down can actually be detrimental to coral growth. 

You can read about it and how to calculate DLI here:  https://www.advancedaquarist.com/2009/5/aafeature

I know, cutting edge from 2009 but it is kind of proof that many hobbyists get distracted by shinny things or over simplify things. 

Anyways, once you calcualte your DLI you will be like... [language filter]??  My DLI is 8.2 (that is mine) and in nature its 30-40??  Don't go cranking up your lights yet, as it is more about spectrum.  This is a REALLY good article that I referenced above talking about what color of light is in the ocean as opposed to your aquarium. To me, it is also a very good example of why to run carbon, water in your tank gets yellow (yes, more yellow than you probably think, fill a clear glass full of tank water and look down through it at a white piece of paper.  The article is here: https://www.advancedaquarist.com/2013/12/lighting

It didn't really click for me until my drive to work this morning...yes, I have a hard time shutting my brain off... the likely reason why we can not blast our tanks with an equal amount of light as the ocean is lots of that intensity is GREEN light, which, does not drive photosynthesis in corals..or plants for that matter.  There is an article that discusses the different wavelengths of light and which are absorbed by corals and which are not.  It is here:  https://www.advancedaquarist.com/2014/5/aafeature

So... the reason our DLI is soo much lower than nature, and why you should never try to emulate natural light volumes is that most, if not all, of our lighting systems are heavily biased towards the blues.  This is why I have blue reefbrites and three actinic bulbs over my tank, these are the colors that drive a lot of photosynthesis, my MH supply the rest of the wavelengths. 

DLI doesn't take into account different intensities and time, meaning 4 hours of 600 par is not the same as 24 hours of 100 par, or vice versa (you can't blast your corals with 2000 par for an hour and call it good) it does provide a very good starting point for dialing in your lights.  

I hope some of this makes sense and I am not completely stating the obvious but several people asked me about my lighting at the last meeting.  

(And no, there is no such thing as X-Large PAR)   lol

 

 

 

 

 

[albertareef]

Thanks Brain.  I think this touches a bit on the more pragmatic discussion we had around SPS keeping at Golden Basket during a meeting a while back.  During that conversation, Rudy made a point about ratios (blue/white) and time (I think he ran at least 12 hours on).  Wish we could have captured the info from that conversation in some way as I think it probably was highly related to the more technical pieces you are touching on here.

[The ReefBox]

I think what you may be referring to Brian is photo inhibition  (too much too long)

[pdxmonkeyboy]

7 minutes ago, viper55 said:

I think what you may be referring to Brian is photo inhibition  (too much too long)

photo saturation and photo inhibition, yes.   There have been studies but I believe they were only done for certain species and certain intensities.