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Aragonite Overview
Richard M. Greenfield
Marine Geologist
V.P. CaribSea Inc.
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Aragonite, though ubiquitous in the shallow water tropical marine
setting,
is a relatively rare mineral overall due to its tremendous instability at
surface temperature and pressure conditions. This instability insures that almost no aragonite is preserved under emergent conditions such as the average calcite mine. Calcite as limestone however, is extremely common, covering 40% of the earth's surface. Nearly all aragonite in the world is produced by living creatures in shallow seas. These animals such as corals, specialize in creating a skeleton of calcium carbonate with absolutely as little energy expended as possible. It appears as if aragonite depositing organisms create their skeletons by altering the pH upwards either in their tissues as do corals or in their boundary layer as I believe coridacean algae such as the genus Halimeda do. This is the result of the photosynthetic activity of algae's which produces a net surplus of oxygen thus shifting pH upwards if this surplus is somehow contained such as by the semi-permeable membrane of a coral polyp or in the minuscule dead water layer that surrounds all objects immersed in water.
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Since, in sea water, supersaturation for calcium carbonate (by increasing the pH) results in the precipitation of aragonite these animals are able to build a skeleton with little or no energy expended on the task. The eroded skeletons of corals and Halimeda coridacean algae comprise the majority of aragonitic reef sand grains in the 1 to 4 mm range.
Aragonite naturally occurs in two smaller grain sizes as well. Oolitic aragonite is thought to be formed either as a direct chemical precipitate from sea water or by the mediation of a microscopic coating of blue-green bacteria/algae (in the same manner as described above). Since virtually everything in tropical seas are coated with bacteria, the exact mechanism for precipitation of aragonite in oolitic form is difficult to pin down and has been debated by geologists for nearly half a century.
Still more aragonite is floating free in the water column of tropical seas in the form of 1 to 10 micron crystals. This, until recently, was considered a clear case of direct chemical precipitation from sea water due to it's trace element signature (approaching 10,000 ppm strontium and the Sr/Mg ratio) but with the discovery of aragonite fixing free floating bacteria nobody knows what to think!
Several chemical properties make aragonite the ideal material from which to manufacture a high performance substrate:
1) Aragonite is metastable at a pH of 8.2 i.e. it begins to dissolve into its
constituent ions of Ca++ and CO3-- while calcite (typical "crushed coral")
begins to dissolve somewhere in the mid 7's.
2) Aragonite contains substantial amounts of the larger ionic radius +2 cations
such as strontium (up to 10,000 ppm) which are released into the system as the
substrate dissolves. Under laboratory conditions the presence of strontium in
solution appears to facilitate the inorganic precipitation of aragonite when
those solutions also contain sodium and magnesium (like sea water). This would
seem to confirm the observations of hobbyists who note an acceleration of coral
growth with the addition of strontium to a closed system.
3) Unlike calcite, aragonite continues to react chemically with sea water after
acquiring a bacterial biofilm coating. There are further ways to boost the
performance of aragonite. The physical properties of the material can be enhanced
by close grading which allows for more interstitial water per volume, and by
manipulating the surface area to volume ratio which states that if grain size is
uniform, the surface area as a function of volume increases as the grain size
diminishes. Finally, performance can also be increased by technological means
such as by a calcium reactor or the Eco-Sand plenum system. This combination of a
superior raw material boosted by mechanical and technical means is simple and
effective and lasts for the life of the system.
What kind of magic potions could we use to make corals grow faster? If there were just something that we could add to the water to really make our coral cuttings grow faster, we could make a lot more money growing corals for sale from small cuttings.
Well, you could raise your temperature a little to speed up metabolism and get faster growth, but only to a reasonable point. About 80-85 degrees seems to be the limit depending on the type of coral.
Trace elements help, but only to a certain point also, then they cause toxicity problems and excessive algal growth. Reef Janitors can help with the algae part though.
Circulation is very helpful to some corals, but only if you don't blow them right over. Lighting? Maybe more lighting?
As I sat thinking of ways to speed up the growth of corals and mushroom anemone cuttings I realized that my optimistic plans for doubling the number of cuttings I can grow each month by re-dividing them on a pre-set schedule usually doesn't work as planned or hoped for. In other words, the coral cuttings don't cooperate as well as I want them to all the time.
I dream up optimistic multiplying schedules which sound great, but the corals sometimes grow fast and sometimes they slow down. I found that the best you can do is optimize everything you can and then be patient. Sometimes A coral cutting doubles in a month and the next time I divide it, it takes two or three months to double. Don't count your chicks before they hatch and don't spend your money before your coral cuttings double.
Take for example a leather mushroom coral (sarcophyton). Initially I can cut an inch wide ring off the outer disk and then cut it into a bunch of one inch squares. I can attach these by sewing, super gluing with Super Reef GelTM or letting them sit in a coarse gravel bed to attach to small pea sized chips or chunks of rock. Then I glue these attached pebbles to a chosen rock to attach the coral.
But some times the new cuttings skin over and go into an unusually prolonged dormancy cycle. For this reason I learned to not use phosphate remover ever just before or after making sarcophyton cuttings. Phosphate remover can especially cause havoc when leather corals (and some others) are trying to attach to new rock. The process just slows down.
If you take too much phosphate out of the water to combat hair algae and cyanobacteria, you not only slow down the growth of hair algae but the growth of everything. Constant overuse of phosphate remover will help me get a beautifully clean tank that is slow growing with dead sarcophyton corals after a while. So, too much phosphate slows down coral skeletal formation and too little phosphate starves corals. Should we dose phosphate?
Wow, I can almost hear a commotion out there already.
If we could dose just small but healthy doses of phosphate into a phosphate deficient system then maybe we could control it and get good results. Did I hear someone say: "Oh no, not another piece of equipment?".
No, it's not another piece of equipment. How about just an additive instead? I think I heard another groan: "Not another additive, I use 15 of them already!". Well, just try using some simpler additives that have most everything combined already. Then you'll have room for a couple of goodies like Magic Reef DustTM and Coral VitalTM. I have seen and heard of Coral Vital helping in many instances as a supplement.
| This amount is perfect for dosing a 55 gallon aquarium according to Sally Jo Headlee. Living proof of how well it works is in her 55 gallon reef aquarium. It is amazingly beautiful! Those who have had a chance to watch it grow will attest to its unusually fast growth rate. |
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She adds a capful of SeaChem's Reef Plus every
other day and gives it the Magic Reef DustTM treatment weekly. After dosing with Magic Reef DustTM, the reef aquarium looks quite cloudy and mucky for hours. When it clears after 6-12 hours, the aquarium water is unusually clear and the corals all perk up. I'm sure it has a similar effect to adding SeaChem's Reef Builder to the tank, but this seems to do even more. |
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Besides adding calcium carbonate, it adds lots of trace elements including phosphate which no one would dream of adding to a reef aquarium, right? Once diluted in a whole aquarium full of water, the actual dose is quite small and controlled though. The reason I really think that the phosphate it provides is helpful to many corals is as follows.
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After using Magic Reef DustTM "on and off" for about a half year, I started
noticing that after I used it, sarcophyton corals and their cuttings that
were in dormancy, skinned over with retracted polyps, would usually come
out of dormancy the next day! Kind of the opposite effect as using too
much phosphate remover for too long. This isn't a guaranteed cure but it really helps most of the time and all the corals appear to benefit. It probably isn't just because of the phosphate in the dust. |
 leroy@garf.org FOR SAMPLE ORDER.
Propagation notes on Mushroom AnemonesOtto Segura Ph.D.os@eng.buffalo.edu After loosing many cuttings to slime, protozoan infection, I decided to cut the mushroom into four pieces like a pizza pie. After cutting them and let them heal first, until they are fully healed, in my opinion, when the disk is fully form, this will lead to stronger cuttings. TRITON AND BLUE MOON 40 WATT BULBS  When the cuttings are fully formed remove all of then with exception of one, this will provide more cutting in a few weeks. The cuttings should be removed with either a sharp razor blade or scissors. Make the cut bellow the disk as close as possible to the base, these cuttings are much stronger than cuttings done of just the disk of the mushroom, even if these cuttings are not attacked by protozoans. After the cuttings have been removed, dip then in a small cup of the aquarium water with a few drops of iodine for about three minutes. I found out that after about two days that most of the cuttings detached by themselves. Once this is done, put the cuttings into a gravel bowl, as described by Leroy Headlee in the home page of Garf. Editors note - This method of cutting seems to improve on the other ways we have done it. Please report any data you collect.
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