With so many sources of coral available on line these days, and so many different lighting formats, it’s more of a challenge than ever to acclimate your new purchases to your specific lighting regimen. There is, unfortunately, no single “sure fire” way to make sure that every coral that you acquire will adapt to your system; however, there are some time honored ways to give them the best possible chance.
First off, when you are coral shopping, be it online, at an LFS, hobbyist frag forums, or even the club frag swap, the very best way to start out is to simply ask the vendor what the lighting conditions are in the system in which the coral you’re purchasing comes from. You want to get as much information as possible, such as what kind of lighting, how long a photoperiod, how many watts, and how far off the surface the lighting is. In the case of LED’s, with infinite possible color and intensity settings, its easier than ever to ask the growers what his or her settings are.
Tons of coral choices- tons of possibilities!
Before you pull the trigger, and order the corals, you need to give some thought about where you will be placing your new pieces in your system. Obviously, high-light loving corals like Acropora robusta, hyacinthus, etc. need to be placed on your reef structure in an area where they will receive the most intense lighting possible. Corals such as Chalices, many Acans, and other Blastomussa generally tend to favor slightly more moderate lighting, so you need to make sure that you have a spot in your reef that you can locate the coral long term.
Assuming you have done your homework and pull the trigger, when you receive your corals, you simply don’t want to plop them down in their ultimate spot on your reef from day one, particularly if you’re utilizing a different lighting format than the vendor. Shocking the coral is an all-too-real possibility.
What kind of lighting did they come from? A key piece of the puzzle!
You can start out by placing the coral farther down on the reef structure than it will ultimately be placed, and moving it up over a period of 2-3 weeks. Alternatively, some reefers use widow screen or even light diffuser (eggcrate) underneath their lights, gradually removing it over a period of a couple of weeks, effectively ramping the light up. The only downside to this practice is that such measures affect all of the corals in the reef, which could actually prove counterproductive to the ones already settled.
You can also take measures such as raising your lighting fixture higher over the aquarium, then gradually lowering it back into its original position over 2-3 weeks or so. This is an alternative to moving a coral up the reef structure. Once again, it suffers from the downside of forcing resident corals to make adjustments as well. A trade off.
Still another method used is to manipulate or reduce your photoperiod while acclimating new corals. What do I mean? Well, let’s say your lighting period is like 10-12 hours per day, and hits it’s maximum intensity around 1PM, and runs at this level for 6 hours. You could consider reducing significantly the maximum intensity portion of your photoperiod to say, 4 hours, and then running a far more reduced intensity for the rest of the day. I sound like the proverbial “broken record”, but again keep in mind that you’ll be making the “resident” corals make some adjustments, too, to accommodate the newcomers.
It can always bounce back more easily from "LESS" light..right?
LED’s have acclimation modes, which, in theory are great, and do a lot of the fancy adjustments for you. Of course, you should consider once again the impact of such adjustments on the established “resident” corals. Seems to really be no avoiding that! Acclimation is not always a perfect science. It involves trade-offs and sometimes tough decisions. In fact, switching form another lighting format to LED requires careful consideration, and should be done slowly. Start with an intensity somewhere around 25-30% and then gradually ramp up over an extended time period, by say, 5% per week until you achieve your desired intensity, whatever that might be.
Although I keep going back to the idea that even the resident corals will have to make adjustments if you manipulate photoperiod or intensity while acclimating new corals to you system, in my experience, and the experience of many others- the trade off of slightly reducing intensity and photoperiod while acclimating new corals to your lighting is tolerated far better by all of the corals involved than by simply tossing the new coral under the current lighting and expecting it to acclimate. In other words, corals can handle periods of reduced lighting way better than they can handle radical shifts to much higher lighting intensities.
Err on the side of caution.
One of the most common questions we receive concerns what to do about our Acros, which come from systems illuminated by 400 watt 20k metal halides. Many aquarist are now using LED’s and wonder what the impact will be on the coral, and where to place them. The main difficulty in providing an answer is that there is no absolute answer! We simply don’t grow our Acros under LED’s, so they will be making some sort of adjustment. Do consider that LEDs are wickedly intense, and many an Acro, even coming from high-powered halides, has been essentially fried by improperly acclimating them to their new lighting regimen. Dramatic increases in PAR are quite stressful for any coral. Kind of like jumping off the plane on day one on your Hawaiian action, putting on SPF5, and then laying on the beach for 8 hours…only the consequences could prove much worse for the corals…And they can’t even roll over!
Just remember, they can't move on their own!
Adjustments simply need to be made slowly, period. There is, in our experience, no real shortcut to this. You simply can’t ask an animal to make a super fast adjustment to a radically different lighting scheme and expect it to thrive. Err on the side of longer acclimation periods, IMHO!
Coral bleaching occurs for a variety of known reasons. In relation to this discussion, it occurs when a coral divests itself of its symbiotic zooxanthellae (the algae in the coral tissues that gives it color). Corals can be stressed acclimating to higher light intensities, and their rate of photosynthesis is much higher than before, causing them to be supersaturated with free radicals and free oxygen, which are toxic to the coral. The coral tries to compensate by producing chemicals that destroy the excess oxygen, but this also produces, among other things, hydrogen peroxide, which is problematic and must be eliminated by the coral. If it can’t do this quickly, out go the zooxanthellae, and the coral will simply waste away and die because it can’t produce enough energy to survive. Not good.
Spectrum IS important, too. Let’s face it- we’re in a “windex phase” in the reef hobby, with everyone seemingly fixated on providing crazy blue disco lighting in order to enjoy the fluorescence of the corals. If you can acclimate your corals to this type of light and get some growth, more power to you. The problem is that you are also asking your new corals to make yet another accommodation- a spectral change…Something that can cause the animal significant stress, so it must be done quite gradually- a tricky thing to do. And the reality is, not all lighting is “nutritious”- i.e., the spectral choices that make the corals look all pretty may not be the best ones for them -or more specifically, their resident zooxanthellae.
Corals produce pigments to protect their zooxanthella and their tissues, and radical lighting changes can alter the formation of these pigments, resulting in not only a potentially stressed-out coral, but one that may have radically different coloration than when you first purchased it! This is at least a plausible explanation for why we often see “color shift” in captive corals, generally attributed (and at least partially correctly so) to the lighting used in the aquarium.
Something to think about.
For wild corals, it’s an even rougher adjustment. You’re talking about an animal that has for eons adapted to life in a specific natural environment, with predictable and stable lighting conditions, and then suddenly, one day- BLAM! It’s yanked off of the reef, thrown in a box with other corals, held in a facility, then thrown in another box on a plane to the LA wholesalers or you coral vendor, forced to acclimate to a totally artificial lighting scheme after days in a box. Then, some time later, it’s sent on to the aquarium retailer or, if it’s lucky- to its finally home in your aquarium. That’s a LOT of adjustment that a coral has to make in a very short amount of time! An we’re only talking about lighting here!
In the end, the acclimation of corals to different lighting regimens is a completely imperfect science, fraught with gaps in our knowledge, tradeoffs, big gambles, outright guessing, and some luck. In my opinion, there is simply no real “best” way to acclimate a coral frag or colony to a new lighting regimen. The age old advice about doing it very slow is really the “best” way to accomplish this.
I’d love to hear your thoughts on this somewhat controversial and impactful topic.
As always, think about the needs of your corals, make adjustments based on information- and above all-
Stay Wet.
Scott Fellman
Unique Corals
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