Last Updated 10-9-19
Acropora Coral is one of the most vast coral groups. They are a member of the Acroporidae family, Subclass Zoantharia and the Order Scleractinia.
Their group makes up one third of the ‘reef building coral’.
Out in the Indo-Pacific and the Atlantic, these coral are the largest group to make up corals with usually first being on the building scene of a reef. Once this hard coral is in place, other softer corals start their placement.
In the ocean, the Acropora are also one of the most tolerant when it comes to water temperature, current movement, salinity, and lighting.
Even with their ability to adapt in the wild, they still often prove to be difficult to keep in captive.
Acropora come in a massive verity of sizes, shapes, growth formations, and colors. It is all depending on their species, which there are over 400 of.
They are a small polyp stony coral (SPS) that have a very thin flesh covering their calcium base bodies.
They also are referred to as table coral, elkhorn coral, or a staghorn coral. This is because of their appearance and because the form a table top like structure when growing with other corals.
On the branches, the small polyps have mouths surrounded by small tentacles for feeding. These branches form a great habitat for other reef creatures to live such as crabs and fish.
The shape of Acropora is depending on its location.
The coral that is closer to turbulate waters will be thicker, while the coral that is out in calmer water will be longer and thinner.
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Other shapes can be things like plates, columns, ridges, bushes, fingers, or clusters.
When it comes to aquariums, the table tops species of Acropora is highly sought after, but also one of the most difficult of these species to keep. Because of these common characteristics, they are the easiest coral species to identify. They have a distinctive skeletal texture which is referred to as Reticulate Coenosteum.
All most all of the species of Acropora come from the Pacific, with just three species that come from the Atlantic. Despite their delicate looking shape, they are mostly found on the upper reef slope were the wave action is strong. When these corals are broken, they will form a new coral asexually from the fragment.
Colors of Acropora come in about any color that you can image. The color is depending on the location of the coral, but how they form the color is all the same. They all have a zooxanthellae marine algae which resides in the corals skin. These zooanthellae range in a wide variety of fluorescent pigments.
Acropora do have similarities to a few other coral species. They are sometime confused with Cyphastrea, Anacropora and Isopora.
Acropora species in general reach sexual maturity with three to five years and have a life span of four to seven years. They can reach an average height of 20 inches, with a branch diameter of 4-7 cm. (1.5″ to 2.75″).
Depending on the species of the coral, they can reach upwards to 10 feet.
They are actually considered a fast growing coral due to their high metabolism. If fed properly along with correct maintenance, these coral will grow just as fast in captivity.
As these coral grow upward towards the light, the branches and all polyps also point upward making a tree like structure. If any of the individual branches break off and land in an undisturbed place, a base may form and new branches will appear.
The same principles apply to captivity and propagation.
Reef keepers can clip off a branch and apply it to something sturdy like a frag plug or rock. A new coral will form.
In young colonies of branching forms of Acropora that form tables or plates; if they are located in a place with a higher current or wave action, the coral may be encrusted because the base will form before the branches.
Keeping Acroporia Coral
Keeping Acroporia Coral can be a big endeavor. The aquarium keeper should have experience in marine aquarium keeping before starting out with these hard corals.
Even better would to already have some reef keeping skills. Having these skills will be invaluable for keeping hard corals alive.
Even though many people keep these corals and in the wild they are generally tolerate, these corals are still sensitive to temperature changes, low lighting, and water movement. Even just moving them around the tank can cause them to die.
Here are the best requirements for keeping these corals.
In general they like water movement, medium to high lighting, and need to be maintained correct levels of Calcium, Magnesium, and other trace elements.
Pristine water quality is important for this coral to thrive.
Move movement needs to be lighter as the Acropora first start out.
As they start to grow, flow can increase.
As the coral grows denser, the water flow will slow greatly. More flow will be needed so it is a great idea to have a variable flow pump. Something that can be adjusted higher and higher. It needs to be a surge like water movement.
Acroporia prefer strong random, mixed water current. A rotating power head or wave maker are also recommended.
The Seio line or Hydor Koralia are excellent pumps for this application.
Merchandise Link: Seio Propeller Pumps
Without a stronger flow, corals tend to develop infections caused by waste built up on the coral. This becomes a breeding ground for bad bacteria leading to problems.
Calcium and Alkalinity–
It’s imperative to keep adequate levels of both Calcium and Alkalinity.
Calcium needs to be kept at 400-420ppm and Alkalinity needs to be kept at 8-9dkh.
Some people who keep SPS corals suggest keeping the corals at higher KH will increase the color.
Having a balance around 450ppm for Calcium and KH at 10 are the suggested levels. This will provide high amounts of what is needed for Calcium and Carbonates to growth.
If the Acro does not have enough calcium, it will not grow. There will be no tissue recession, but the polyps will be extended. If there is a low amount of Calcium, raising the levels will almost always cause a rapid spurt of growth if all other parameters are good.
While cheap/bulk methods of supplying calcium and alkalinity have grown popular of late due to a popular online reef supply retailer, I recommend avoiding the “cool kid club” and going what is more science based such as the “Balling Method”
Magnesium needs to be around 1350-1500. Magnesium makes calcium available, so if your calcium is low, check your magnesium levels before adding any more calcium.
Phosphates need to be kept as low to zero as possible. Elevated levels will cause the new growth to come to a stop. Many reef keepers use and recommend to run a Phosphate remover. These include products such as AAP/SeaChem Phosbond, AAP/Rena Phos-Zorb, or NPX Bio Plastics (in FSB Filter or reactor chamber)
Of course the Nitrate levels need to be kept as low as possible as well. Any amount that can be detected on a standard aquarium test kit will cause a browning of the coral due to a rapid reproduction of Zooxanthellaes.
Good lighting IS KEY for coral growth. 6500K -20K lamps are the most effective for sustaining coral life, depending upon species, depth, & light source PUR/PAS.
The blues provided in these higher kelvin provides the useful light energy (PUR) needed for symbiotic Zooxanthellae found in the coral.
Bluer color lighting is required for deeper waters. Blue light penetrates waters deeper. Anything light that used that’s not at the optimum levels needed will cause additional Zooxanthellae to compensate for the loss nutrition.
With quality LEDs now more of a commonplace than as recently as 2010, finding a good/adequate LED should not be a problem. However many of even the better LED fixtures still compensate with cool white and many other less than optimum emitters in combinations and quantities to make up for poor PAS/PUR resulting in higher wattages and PAR readings being used than would be necessary with the few LED fixtures optimizing output using licensed/patented emitters, PWM, and more for more efficient fixtures for the same results.
Often the need for cooling fans is a telltale sign of this problem, which also is a part that fails and thus severely shortens the life of the LED fixture.
Specimen placement according to lighting depth penetration, as well as water movement is also important.
With poor levels of light, the coral will almost stop growing completely and will most likely die. The market standard for reef lighting are Metal Halide and “high end” LED (not the mass market brands).
Recommended Merchandise Link: AAP AquaRay Super Premium LED Aquarium Lighting
Note that AAP is the ONLY North American authorized online full service retailer of the Aquaray lighting line of products, despite Google bringing up an official sounding website selling out of a residence!!!
Below is a picture of a reef aquarium containing acropora corals that has been running for 6 months as of the time of this picture with AquaRay/ AquaBeam NP 1500 and 2000 LED tiles ONLY!
The Coral Colour Plus 1500 is another popular LED from the industry leading AAP AquaRay line of LED Lights (based on science, not social media popularity).
Saltwater strength should be around 10.25/26 with good filtration and water quality.
Temperature and pH–
Two things that will destroy any aquarium before you know it is temperature and pH swings. These are very stress for fish, plants, and corals all alike. Keeping a constant temperature and pH is essential for optimal growth. The best pH is 8.3. Temperature needs to be in the range of 72-83 F (22.2 to 28 C)
Acropora does best in an aquarium 100 gallons or larger, with other fish to generate organic matter. The aquarium needs to be as stable as possible, so it is even recommended that the aquarium be matured to a year before placing coral. It is also recommended to start by placing all the coral you would like in the tank all at once, so that if another coral is introduced into an established aquarium, a disease in the new coral wont wide up the whole tank.
If the aquarium is started from new coral frags, which most are, it can take up to six weeks before new growth of a nobe are seen. It takes five to six months for Acropora to regain their normal growth rate.
Doing water changes of 10% every 2 weeks is needed, although it is suggested that doing 5% water changes once a week will bring about amazing results. Keep the nitrate levels low.
Acropora corals have a symbiotic relationship with light sensitive marine algae known as Zooxanthellae. Much of their nutrients are from these Zooxanthellae.
While Acropora have been shown to extract nitrogenous compounds from the water column for their amino acid needs, supplementation has also been shown to be highly beneficial for growth, vibrancy and over all health in a closed aquarium system
Reference: Amino Acids
Recommended Merchandise Link: AcroPower Amino Acid Supplement for Coral
Feeding of these corals is done at night. This is why the tentacles come out and feed on the ocean debris from the ocean floor.
In captivity, it is recommend to feed about once a week.
The Acropora corals are peaceful, but watch out for crabs.
Many experienced aquarists do not believe any crab should be kept in a closed system with Acros. Crabs are opportunistic predators, with the exception some of the symbiotic crabs like commensal crabs, and gall crabs.
SPS Coral Ailments
There are various ailments that small polyp stony (SPS) corals fall victim to. Several ailments are often named for what they look like, such as white plague or yellow-blotch.
Here are a few SPS coral ailments and some treatments that may help:
Source: Animal-World.com; Keeping Acropora Corals
- Rapid Tissue Necrosis (RTD)
Sps corals have been know to have rapid tissue necrosis (RTD).
This is a peeling of the tissue from the skeleton. The causes can be pretty much anything, such as any change in temperature, salinity, or lighting. RTD is easy to spot, if your coral starts to slough off flesh from the bottom up, it has RTD.
Something that can help is to frag the coral. Break it well ahead of the deteriorating coral, thus possibly saving the tips or branches.
- Black Band Disease
Black Band Disease is a dark band moving across the surface of coral colonies, leaving behind exposed white skeleton. To fight black band disease, and prevent necrosis, the corals can be treated with Doxycycline at 10 mg per quart/liter according to one author.
- Brown Jelly
Cyanobacteria and brown jelly infections can be treated with Neomycin sulphite, Kanamycin and other broad-spectrum antibiotics.
The powder can be mixed with sea water to make a paste, and then applied to the wound, or affected site of the coral with a simple artists brush.
Bleaching is the rapid growth of zooxanthellaea. Anything can trigger it and it generally will take the aquarist by surprise. The coral is still alive but with pigmented tissue.
To prevent bleaching if your tank experiences a temperature hike, turn down your lights. This is so the zooxanthellae does not expel out of control. Otherwise once bleaching occurs, it has a 50/50 chance of complete healing. The coral will be prone to illness at this time.
- Acropora Mucus
Acropora corals tend to produce mucous nets that can be a way to eliminate their waste or capture prey. Unless it looks unhealthily, leave the coral alone.
Product Reference: API Doxycycline (Fin & Body Cure)
- Reef Aquarium Chemistry Maintenance
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