Acanthophyllia Coral Care
Acanthophyllia are a large polyp stony coral often referred to as a donut or meat coral. They are similar in appearance to Scolymia/Homophyllia or Cynarina in that they are a single polyp, round in shape, and often times come in some dazzling colors and patterns.
Seven years ago, I did a video on this coral and the title was something like “Acanthophyllia are an underrated LPS.” These days that could not be further from the truth. Nowadays, Acanthophyllia are highly desired among collectors of large polyp stony corals and I would go as far as to say that they are the absolute pinnacle for those looking for that signature show piece.
The obvious downside to that level of demand is the price point for these guys. They are some of the most expensive corals in the industry.
Luckily despite the prices, Acanthophyllia tend to be one of the more hardy corals out there. There are some corals that are notoriously sensitive and it is always a scare to drop serious money into a coral that is known to be challenging. Acanthophyllia are the opposite end of the spectrum. They can be housed in a wide range of tank conditions and can handle a modest degree of neglect. You really can’t say that about a high end Acropora for example.
The only thing I would mention about its hardiness is when it comes to shipping this coral. Shipping is always a stressful event for any coral but it can be particularly damaging for Acanthophyllia. Under all that flesh is one of the spikiest skeletons I’ve seen on any coral. This is troublesome for two reasons, the first is it can poke through shipping bags thus causing leaks and if you are shipping in cold weather, the leaking water can deactivate the heating packs in the box. Big yikes. So when it comes to packing these guys we don’t skimp on the bags. I know I’ve used up to four giant 3-mil bags to send them out.
The second problem with their spiky skeleton is that they can damage their skin during transit. Evan assuming they don’t punch through the bag as they roll around, the spikes skeleton does poke through their skin. Like I said though, it is a good thing this coral is pretty tough because it does not take long for the coral to settle into an established reef aquarium and heal over that damage.
Acanthophyllia are found throughout Indonesia and Australia. The specimens from Australia are predominantly that greenish blue mint-chocolate chip appearance. The specimens from Indonesia are mostly red and blue, but there are rare color variants that are all the colors of the rainbow. Those are the most desirable.
Depending on the colors high end collectors are willing to pay well into the four figures, and occasionally I see a truly stunning piece that I can imagine someone spending a fortune on. Part of the reason for their scarcity is their availability in some countries. Right around the time of the Indonesian export ban in 2018, there were changes in what corals could be sent where and from what I understand Acanthophyllia was one of the most restricted corals once things opened back up.
Here in the US they are still being brought in, but the prices are much higher than before. As for the future of the imports and exports for this coral, that remains unclear.
The other aspect affecting its price is the fact that there are no good aquacultured sources for Acanthophyllia. They cannot be cut and sexual reproduction hasn’t been accomplished on a commercial scale. Hopefully that changes in the future! That would be game changing, but we are talking about a monumental challenge given the difficulty associated with sexual reproduction on the commercial scale and the incredible slow growth of this coral.
That’s a little bit of background on Acanthophyllia. Let’s now talk about their care requirements starting with lighting and placement.
We primarily keep Acanthophyllia in low to medium light intensity here at Tidal Gardens which is around 50 to 100 PAR. We have kept them in higher lighting but they did not appear to appreciate it and were always at risk of bleaching out. If you have a colony of Acanthophyllia and want to experiment with higher light, remember that it can be a risk, so be prepared to move it into a shadier region of the tank at the first signs of trouble.
As for placement, almost every tank I see these corals in keeps them at the bottom of the tank regardless of whether it has a substrate or bare bottom. They settle in nicely down there are when they are happy will extend nicely and take on that Chili’s lava cake appearance. I suppose there isn’t a good reason that they couldn’t be put up on a rock scape, but it is much less common. Perhaps the thinking is that higher up on the rock scape would expose the coral to more light and more flow which might not be the best combination for this coral.
One other thing about placement to consider is to consider how much it will spread out once it settles into your reef tank. Acanthophyllia do not grow fast AT ALL, but they can swell many times larger than their skeleton so you want to avoid a situation where this coral reaches out and covers its neighbors.
Lighting is a loaded topic, so for a more in-depth discussion of lighting, please see our Deep Dive article.
Let’s move on to water flow. We touched on it briefly in regards to placement, but I would prioritize finding an ideal location with regard to flow more so than lighting. Being such a fleshy coral you don’t want to give it too much flow to the point that the skeleton starts to poke through the flesh. It can absolutely happen if the Acanthophyllia is getting hit continuously by a strong laminar flow.
As a general recommendation, I would keep an Acanthophyllia in a low to medium flow area and preferably one with variable flow patterns so one side of the coral doesn’t get hit constantly. Normally I would be concerned about a coral placed on the bottom collecting detritus, but that is more of an issue with small polyp stony corals or large polyp stony corals that grow into a bowl-like shape. Acanthophyllia don’t have any difficulty shrugging off detritus that settles on them so they can be kept in lower flow than most without issue.
The lower flow also makes it much easier to feed.
If you enjoy spot feeding your corals, you are in for a treat. Acanthophyllia exhibit one of the most dramatic feeding displays when it opens up. They practically turn themselves inside out to completely transform into a giant seafood receptacle.
They can be fed a variety of foods, so I wouldn’t overthink it too much when selecting something to give them. LPS pellets or full sized krill would work fine. We’ve even fed them larger items like silversides in the past.
What is kind of strange is how Acanthophyllia reacts to different food. One behavior I’ve seen is that it reacts the most enthusiastically to really small planktonic foods especially frozen rotifers. The colony opens way up but it is hard to tell if it is actually eating anything. I have a feeling that they are taking it in through their mucus coat it is just that their tentacles are not engaged in prey capture during that time.
Once it is fed larger chunkier food though it actively takes them in.
Another thing you can do in terms of feeding that isn't completely necessary, but will help keep your corals on the healthier side, is to feed them amino acids as well
Amino Acids are simple organic compounds that play a major role in building proteins as well as other biological functions at the cellular level. There are a little over 20 different types of amino acids. Most of them can be synthesized by the organism but some cannot be and must be taken in by feeding. Those amino acids are termed essential amino acids and they vary from species to species. Corals regularly take in available amino acids from the water column so it is easy to provide them with adequate quantities by broadcast feeding an amino acid solution. They are available from any number of commercially available reef supplement manufacturers. This may be the easiest way to feed your corals because as long as amino acids are bioavailable in the water column, the corals will soak them up. If you want to know more about amino acids, I made a video going into great detail about them so check that out below:
Moving on from direct feeding, let’s talk a little bit about water chemistry. Because Acanthophyllia are stony corals, there are three major chemical parameters that are needed to support that skeletal growth. Those are calcium, alkalinity, and magnesium. Acanthophyllia are one of the slowest growing stony corals and seemingly take forever to grow a larger skeleton. In that sense, they do not soak up these compounds as fast as a forest of SPS that double in size every month.
Starting first with Calcium, it is one of the major ions in saltwater. In the ocean, its level hovers around 425 parts per million (ppm). As a coral grows calcium is absorbed from the water and used to forms its calcium carbonate skeleton.
Alkalinity is probably the most important parameter to pay attention to. It is not a particular ion, but rather a general figure of carbonate availability in the water. Technically it is the amount of acid required to lower the pH of saltwater to the point bicarbonate turns into carbonic acid. If you have more alkalinity, it can soak up more acid. Less alkalinity and you have less buffering capacity making the tank more susceptible to chemical changes.
In practice alkalinity tends to be the parameter that fluctuates the most, so if you can only manage one test, test for alkalinity. In natural sea water, the alkalinity of the water measures around 7 or 8 dkh though most salt mixes these days mix up closer to 8 to 9 dkh. Some aquarists like to overload this parameter a little and keep their tanks around 10 or 11 dkh with the belief that having elevated calcium and alkalinity in the water contributes to faster stony coral growth.
Raising both calcium and alkalinity together can be tricky because of how they interact. Calcium ions and carbonate want to react with one another. Addition of a calcium supplements often comes with a corresponding fall in alkalinity levels and vice versa. If you are experiencing this in your systems, it is normal, but wild swings are not. If you are experiencing dramatic swings of calcium and alkalinity every time you use an additive, you may want to look at your Magnesium levels.
So why Magnesium? Magnesium behaves chemically similar to calcium. It can bind up carbonate ions thus increasing the overall bioavailability of alkalinity compounds in the water. If you are tweaking calcium and alkalinity and getting strange results, you may want to make sure it is not your magnesium level that is low. In the ocean, Magnesium sits at about 1350 ppm.
Natural sea water levels for calcium are around 425ppm, alkalinity is around 6-ish dkh but we tend to shoot a little higher at around 8 dkh. Magnesium is around 1350ppm.
There are still benefits to maintaining consistent levels so we shoot for roughly 425 ppm calcium, roughly 8-9 dkh of alkalinity, and 1350 ppm of magnesium. In practice alkalinity tends to be the parameter that fluctuates the most, so if you want to test frequently, test for alkalinity. If alkalinity is testing stable, it is likely that the other two are in line, but every so often it is good to get a reading on those as well. More data is always welcome.
The only other chemical parameters to worry about are the “pollution parameters” such as phosphate and nitrates. They show up mainly in the food we provide the tank but decaying plant and animal matter in the aquarium can also elevate their levels in the water. We generally shoot for about 5-10 ppm nitrate and .05 to .1 ppm phosphate. I would rather see Nitrate and Phosphate levels on the high side than barely detectable because we have kept them in systems with very high nutrient with little to no difficulties. In some tanks they are in 50 ppm of nitrate and 2.5 ppm of phosphate. Those figures are obviously super high but it is just to give you an idea of how tolerant Acanthophyllia are on the high nutrient side.
Although Acanthophyllia are pretty tolerant to higher nutrient in the water, I would be careful if you are having algae issues at the same time you are adding a new colony. As I mentioned before, their spiky skeleton can poke through their flesh during transit, and although they normally heal very quickly from that damage, I have seen situations where algae can immediately start to grow on the tips of the skeleton thus preventing the healing. It is not too common, but certainly something to keep an eye on if you are struggling with algae issues.
Ok, that about does it for Acanthophyllia. So what kind of tank is Acanthophyllia best suited for? I see it as a show stopper piece in a super high end collector’s LPS dominated tank. They have a beautiful mix of size, color, pattern, and have really cool feeding behaviors. I can totally imagine someone with an insane budget lining the entire bottom of their tank with these corals! And because they are not aggressive to one another, they can be clustered together like that.
We are always on the lookout for new and interesting color morphs of this coral to add to our collection. Acanthophyllia pose a particular quandary for us because half the time we get one we always think… should we just keep this one here as a show piece? They are so hard for us to let go of!
Alright, that’s all from here, until next time, happy reefing.