Going deeper- some observations about "deepwater" Acropora

  1. We all love Acros!

    That’s not even like an opinion. It’s a fact…You just do, and if you don’t, you’re lying. End of discussion. Yup.

    That being said, we sell, and people seem to ask for, lots and lots of “deepwater” Acropora. What is it about them? Their smooth skin, unusual shape, cool colors- or something else? Maybe, the allure of the term “deepwater”, which evokes the mysterious…

    Anyways, since we deal with so many of them, let’s look at a few facts about their care that we’ve garnered since we’ve been working with them.As always, these are just based on our experience, and you probably have 25 different bits of information on them to add- and I expect that you will, ok?

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    The allure of the deep!

    First off, are all of these “Deepwater” pieces truly from deep water? And what exactly does that mean, in context? Well, talking to some of our mariculture suppliers, I am often told that these Acros are found around 60-80 feet down. Deeper than most of us might want to free dive, but certainly not “deep” as in, well you know- the dark abyss. Many are maricultured around 8-20 feet down. If you dive, you know that at 8-20 feet, it’s still pretty darned bright!, and for all intents and purposes, that’s pretty shallow, really. Yes, there are many species found much deeper, but the vast majority that come into the trade are from the depths cited above, and maricultured at much more shallow depths.

    Lighting is the most common topic that we receive inquiries about when we talk about deepwater Acropora. Specifically, how bright and what kind of light. When we first started working with them, we were pretty paranoid, and threw them under diffuse T5 lighting, concerned that our 400 watt halides would bake them. Well, to make a long story short, we started moving them under the halides, off to the side at first, and then right under ‘em-and the vast, vast majority have been just fine. Sure, they will do okay under T5, and you can maintain them beautifully that way. We always acclimate new Acros under blue-shifted T5 first, before moving them to 20K Radium halides, and the deepwater pieces are no exception. Occasionally we will lose a piece during this process, but we feel it’s because of factors other than light (ie; the usual shipping traumas, RTN, etc.). The takeaway here: Don’t feel that you have to throw your “deepwater” Acro into a cave. Just acclimate it to your higher intensity light slowly. The coral will tell you if you’re doing it right.

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    Acropora suharsonoi, a deepwater "poster child"

    Customers ask us if the smooth-skinned deepwater varieties are any less hardy than their heavily-corallite-covered “shallow water” brethren. We have to say that it depends. I mean, some of the “deepwater” species have thinner, more delicate skeletons, and are far more subject to breakage during transport. This is not really a measure of “hardiness”, but it does give you an idea of the type of handling that you might need to give them. In our experience, if acclimated carefully, the hardiness of these Acros is no different than the more commonly encountered varieties. One thing that we have found, however, is that the deepwater varieties seem to not fare as well with full-strength proprietary coral dips as others do, so we typically use either a very diluted dip, or just quarantine and basting with saltwater. Like all of our maricultured Acros, we cut them off the mariculture base which they come on before offering them for sale, as all sorts of nasty stuff lives and grows on those bases.

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    Acropora multiacuta, a deepwater fave!

    What kind of flow do these Acros like? Well, in our experience, they do fine with the same significant flow rates that we keep all of our corals under. Sure, you don’t want to blast them with the direct output from your MP60, but you do want them to receive the benefit of good water movement. The morphology of most of these specimens will sort of point the way: The spindly, thin-branched species are usually not accustomed to super high flow, and may be better suited for strong, indirect flow areas of your reef. The thicker, flatter-branched varieties (A. fenneri comes to mind) seem to be much less picky about where you place them, in relationship to the flow. Like any other coral, the “deepwater” Acros need individual assessment to finalize where they will thrive within your reef. Just observe carefully.

    Other random observations regarding the “deepwater” Acros: They respond quite well to imposed propagation techniques. Although many of them do not encrust on plugs in the manner to which we have become accustomed by say, A. millepora or A. tenuis, they will create a fairly sold base for themselves and grow outward from there. One of our favorite species, A. multiacuta, actually gets a really tight, thick morphology from frags, and colors up very nicely. others, like A. suharsonoi, seem to retain the delicate long branches of the mother colonies immediately. The common deepwater Acropora have very elongated branchlets, spaced out corallites, and a smooth coenosteum. In the wild, these species are mostly brown to tan in color., yet we are seeing more and more nice blues and greens showing up now, particularly in the maricultured specimens! And of course, the “Red Dragon” (A. simplex or A. carduus?) is a “deepwater” species. (of course, there are several species given the popular name, “Red Dragon! LOL).

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    The "Red Dragon"- but which species? Acropora simplex, perhaps? Or Acroproa carduus?

    What are the most common deepwater Acros we encounter? Glad you asked. Here are the ones we usually see in the trade:
    Acropora suharsonoi

    Acropora caroliniana

    Acroproa carduus
    Acropora multiacuta
    
Acropora granulosa

    Acropora lokani
    Acropora simplex

    Acropora derawanensis
    
Acropora elegans

    Acropora echinata
    Acropora fenneri

    Acropora pichoni

    Acropora batunai


    Break out Veron’s book for interesting nature pics of all of these guys. The dive pics will also give you some idea as to their natural occurrences and locales. Good stuff!


    Lots of reefers want to know if they feed like “regular” Acros, because there seem to be no polyps! Well, if you look carefully at your deepwater species, you'll realize quickly that they DO have them, just fewer and more spaced out. Biologist float the theory that a coral extends polyps based upon the “costs/benefits” of doing so, and that, in order for the polyps to be extended, the coral is using energy. So, perhaps, the deepwater environments don’t have quite as much planktonic food, and are perhaps richer in dissolved nutrients which are easier for the coral to absorb, thus requiring less polyps (and therefore less energy) to do so. Interesting, huh? Bottom line, we do see them extend polyps so food sources, be they planktonic or, well, fish poop, are utilized!

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    It eats, it grows, it's attractive and peaceful. Marriage material. Acropora fenneri.

    So, there you have my quick take on the joys of the so-called “deepwater” Acros. They are attractive, interesting, and a lot of fun to keep, and they add (literally) another dimension to your reef aquarium with their fascinating and beautiful morphology.

    No doubt you have your own experiences and theories about these awesome corals, so let’s hear them, ok?

    So for today, go deep…

    And Stay Wet

    Regards,

    Scott Fellman
    Unique Corals

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