A deep dive into identification, natural habitat, morphology, husbandry, and aquarium behavior for three of the hobby’s most misunderstood large-polyp stony corals.

Among large-polyp stony corals, few animals generate as much fascination—and as much confusion—as Acanthophyllia, Indophyllia, and Cynarina. All three are solitary, fleshy, highly ornamental corals that occupy a similar visual category in the minds of reef aquarists: oversized tissue, strong coloration, and unmistakable showpiece presence. In local fish stores and across online coral listings, they are often grouped together under the broad umbrella of “meat corals” or “donut corals,” and that shorthand is understandable. But it also flattens the meaningful differences in structure, habitat, rarity, and aquarium behavior that make each one distinct.

For the reef keeper trying to decide which coral is right for a display tank—or simply trying to understand what they are actually looking at—those differences matter. They influence how the coral should be identified, where it should be placed, how much light and flow it wants, how it should be fed, and how much caution should be used when purchasing rare or high-end specimens.

This article takes a deeper look at the three corals side by side: what separates them visually, what they appear to share ecologically, why Indophyllia remains the most enigmatic of the trio, and how hobbyists can keep each one successfully over the long term.

For readers looking for additional coral examples and husbandry references, some supporting resources can also be found through ExtremeCorals.com’s LPS coral collection and related coral care articles published there over the years.

Why These Three Corals Are So Often Compared

At a glance, the comparison makes sense. All three are solitary fleshy LPS corals with strong display appeal. All three are usually placed in lower-energy reef zones with moderate or gentler flow. All three benefit from stable chemistry, careful acclimation, and occasional direct feeding. And all three are the kind of corals that immediately draw the eye in a mature reef tank.

But they are not interchangeable.

Acanthophyllia tends to be the broadest, most uniformly fleshy, and often the most overtly “meat coral” in appearance. Cynarina typically has a more inflated, doughnut-like or vesiculated look, often with softer transitions between tissue zones. Indophyllia sits in the middle in some respects, but in truly distinctive specimens it carries its own signature: a more structured feel beneath the tissue, a different oral-disc presentation, and the patterned spotting that many experienced collectors use as a clue.

For the newer hobbyist, these differences can feel subtle. In practice, they become easier to see once you stop judging them primarily by color and start looking at body plan, inflation pattern, oral structure, and tissue architecture.

The Shared Ecological Story Behind the “Donut Coral” Group

One reason these corals overlap so much in hobby discussion is that they appear to occupy similar ecological space. Rather than behaving like high-energy reef-crest corals, these solitary forms are more commonly associated with lower-energy, non-typical reef settings—especially sandy bottoms, deeper reef slopes, and open substrates where a fleshy coral has room to sit, expand, and feed.

That ecological background explains a lot about how they behave in captivity.

These are not corals that want to be jammed into the brightest upper rockwork under aggressive, direct flow. Their tissue is too fleshy, too exposed, and too prone to irritation from turbulence or abrasion. In the home aquarium, they usually do best when treated as low-profile benthic showpieces: well supported, fully expanded, and given room to sit without constant mechanical stress.

That is also part of why they are so satisfying to keep. They read less like “background reef structure” and more like individual animals with a defined footprint and a strong visual identity.

Acanthophyllia: The Classic Solitary Meat Coral

If one coral in this trio most fully embodies the hobby image of a premium solitary meat coral, it is Acanthophyllia. Healthy specimens are often broad, thick, and exceptionally fleshy, with tissue that drapes heavily over the skeleton and creates a luxurious, oversized look in the aquarium. The best examples combine dense inflation with strong color saturation—greens, reds, oranges, and multicolor combinations that appear almost painted under blue-heavy lighting.

In visual terms, Acanthophyllia usually appears the most massive and broad-bodied of the three. It often has a smoother, more unified fleshy presentation than Cynarina and a less pattern-driven look than Indophyllia. Its appeal tends to come from fullness, scale, and tissue mass.

Indophyllia: The Rare Outlier With a Collector’s Morphology

Indophyllia is the most intriguing coral in this comparison because it is both the least commonly encountered and the most frequently misidentified. Many reef keepers never see a true Indophyllia at all. Others see one, assume it is simply a particularly unusual Cynarina or Acanthophyllia, and move on.

That confusion is understandable. Indophyllia shares a great deal with the other two in overall life strategy and habitat type. But when a high-quality specimen is viewed carefully, its differences become clearer.

Indophyllia is often regarded as the rarest of the three corals commonly lumped into the donut-coral conversation. It has been associated with deep, sandy habitats and free-living life on open substrate. Morphologically, experienced observers often point to a more structured feel beneath the tissue, a differently organized mouth, and the distinctive spotted or “jaguar” patterning that can show through the tissue in top specimens.

In the best examples, those markings are the giveaway. While color alone can push an Indophyllia toward Cynarina-like territory, the patterned spotting and underlying structure often tell the more useful story.

Cynarina: The Inflated Doughnut Coral

Cynarina is probably the easiest of the three for hobbyists to recognize when it displays its classic form. Healthy specimens often inflate into a rounded, soft, doughnut-like presentation, with bubble-like vesicles and a smoother, more swollen appearance than either Acanthophyllia or Indophyllia. This is part of what makes Cynarina so attractive in the first place: it looks almost unreal when fully expanded, as if the tissue is floating over the skeleton.

In shape and visual feel, Cynarina tends to read as softer and more inflated than the others. Where Acanthophyllia looks broad and weighty, and Indophyllia looks more patterned or structurally specialized, Cynarina often looks sumptuous and ballooned. This quality is especially pronounced in bright pink, red, and multicolor specimens.

Husbandry: Water Chemistry, Placement, and Long-Term Care

While these three corals are different in appearance, their general husbandry overlaps enough that they can be discussed together before getting into the finer distinctions.

Temperature

A practical temperature range for all three is 75–80°F, with many aquarists keeping them most successfully around 76–79°F. More important than the exact number is avoiding instability. Repeated swings are far more stressful than a slightly warmer or slightly cooler but stable system.

Salinity

They generally do best in a reef-standard salinity range of 1.025–1.026 specific gravity. Stability matters here as well, especially because large fleshy solitary corals can respond poorly to abrupt osmotic changes.

pH

Aim for a stable pH of 8.1–8.4. Chasing pH aggressively is rarely helpful, but avoiding chronic low-pH conditions and maintaining good gas exchange is beneficial.

Alkalinity

A practical alkalinity range is 8–9 dKH, with consistency being the key. These are not the kind of corals that reward aggressive chemistry swings. Large fleshy corals often look best when alkalinity is simply kept stable in a moderate range rather than pushed.

Calcium

Target 400–450 ppm calcium. Since these corals do still build skeleton even though their tissue is what usually gets all the attention, calcium should not be neglected.

Magnesium

A healthy range of 1250–1350 ppm magnesium helps maintain broader ionic stability and supports overall reef chemistry.

Nutrients and Water Quality

All three generally prefer clean but not stripped water. A sensible target would be:

• Nitrate: roughly 2–10 ppm
• Phosphate: roughly 0.02–0.08 ppm

Ultra-dirty systems can encourage tissue problems and algae issues, while ultra-sterile systems can sometimes leave fleshy LPS corals looking deflated or undernourished. These corals tend to do well in mature, stable reef tanks with reasonable nutrients and consistent export.

Lighting

All three generally prefer low to moderate lighting, especially compared with SPS corals. A practical working range is often somewhere around 50–150 PAR, though some well-acclimated specimens may tolerate a little more depending on the system.

• Acanthophyllia: often happiest on the lower end of that range
• Indophyllia: moderate but not harsh light
• Cynarina: moderate light with protection from direct intensity

These are not “blast them with light” corals. If in doubt, start lower and acclimate upward carefully.

Flow

All three tend to prefer gentle to moderate indirect flow. They should move slightly or remain clean, but they should not be folded, whipped, or blasted.

• Acanthophyllia usually likes the gentlest overall environment
• Indophyllia appreciates moderate but non-abrasive flow
• Cynarina needs enough movement to stay clean but not so much that its inflated tissue becomes stressed

Placement

The safest placement strategy for all three is:

• On sand or a broad, stable low rock shelf
• In lower to lower-mid areas of the tank
• Away from aggressive neighbors
• With room for full nighttime inflation

If tissue can rub rock, a plug edge, or another coral, eventually it often will. These corals need real space.

Feeding

All three benefit from feeding, even though they can survive largely on photosynthesis in stable systems.

Good food options include:

• Mysis shrimp
• Finely chopped marine meaty foods
• Small pellet or powdered coral diets
• Target-fed LPS foods

A practical schedule is 1–2 times per week for Acanthophyllia and Indophyllia, and occasional to weekly feeding for Cynarina depending on the system and the coral’s response.

The best rule is moderation. Feed enough to support tissue and growth, but not so heavily that the system becomes dirty.

How to Tell Them Apart in Practice

For aquarists who want a more practical field guide, the easiest way to distinguish these corals is to focus on overall silhouette, tissue texture, mouth presentation, and pattern.

Acanthophyllia

Think broad, massive, fleshy, and heavy-bodied. It often looks like the most substantial “meat coral” of the three.

Indophyllia

Think rarer, more structured, and often marked by distinctive spotting or jaguar-like patterning. In top specimens, it carries a visual personality that does not quite match classic Cynarina or classic Acanthophyllia.

Cynarina

Think inflated, rounded, vesiculated, and doughnut-like. It usually has the softest, most ballooned appearance of the group.

Once you start identifying them by body plan instead of color names, the distinctions become easier.

Which One Belongs in Your Tank?

That depends less on prestige and more on what kind of reef you are building.

Choose Acanthophyllia if you want a classic oversized meat-coral centerpiece with broad fleshy mass and strong coloration.

Choose Indophyllia if you are a collector who values rarity, subtle structural differences, and the patterned look that makes true specimens so compelling.

Choose Cynarina if you want one of the most inflated and elegant solitary corals in the hobby, especially if you appreciate soft rounded form and strong fluorescence.

Each coral can be extraordinary. The best choice is not the most expensive one—it is the one whose structure, placement needs, and husbandry profile actually fit your tank.

For aquarists who want to compare examples visually, one helpful reference point is browsing dedicated categories like featured corals or established LPS collections from vendors who photograph individual specimens carefully.

Final Thoughts

Acanthophyllia, Indophyllia, and Cynarina belong together in conversation, but not because they are the same coral. They belong together because they tell a larger story about one of the most compelling coral niches in the reef hobby: solitary fleshy LPS corals from atypical reef environments that combine showpiece beauty with subtle biological differences.

For the reef aquarist, learning to distinguish them is more than an academic exercise. It leads to better purchases, better placement, better care, and a deeper appreciation of what makes each one remarkable.

Acanthophyllia offers mass and extravagance.
Indophyllia offers rarity and patterned mystery.
Cynarina offers inflation and elegance.

Understanding those differences is what turns a collector into a keeper.

FAQ

1. What is the main difference between Acanthophyllia, Indophyllia, and Cynarina?

The biggest differences are in body shape, tissue architecture, and presentation. Acanthophyllia is usually the broadest and most massive, Indophyllia is often rarer and more structurally distinctive, and Cynarina is typically the most inflated and doughnut-like.

2. Which of the three is easiest to keep?

Acanthophyllia and Cynarina are usually more familiar to hobbyists and somewhat easier to place confidently. Indophyllia is often the most challenging simply because it is rarer, more expensive, and more easily misidentified.

3. What alkalinity should I keep these corals at?

A stable 8–9 dKH range is a very good target. Stability matters more than trying to run unusually high alkalinity.

4. What temperature is best for these corals?

A good working range is 75–80°F, with most reef keepers aiming for stable temperatures in the 76–79°F range.

5. What salinity do they prefer?

They generally do best at 1.025–1.026 specific gravity, with minimal fluctuation.

6. How much light do Acanthophyllia, Indophyllia, and Cynarina need?

These are generally low- to moderate-light corals. Many hobbyists keep them successfully around 50–150 PAR, depending on the species, acclimation, and tank setup.

7. What kind of flow is best?

They prefer gentle to moderate indirect flow. Enough movement to keep them clean is good, but direct blasting is usually harmful.

8. Do these corals need to be fed?

Yes. All three benefit from occasional supplemental feeding with mysis, finely chopped meaty foods, or quality coral foods. Acanthophyllia and Indophyllia often show especially strong feeding responses.

9. Can these three corals live in the same tank?

Yes, absolutely—provided the tank has stable chemistry, moderate light, indirect flow, and enough spacing for each coral to fully expand without touching neighbors.

10. Where should I place them in the aquarium?

The safest placement is usually on sand or a stable low rock shelf in the lower to lower-middle tank zones, away from aggressive neighboring corals and strong direct flow.

About the Author

Scott Shiles is the owner of ExtremeCorals.com, which he has operated for over 25 years and is recognized as one of the early dedicated live coral websites on the internet. A lifelong reef keeper since 1984, Scott has decades of hands-on experience maintaining marine aquariums and previously owned and operated a brick and mortar aquarium retail store for 10 years, including five years alongside Extreme Corals. He holds a degree in Marine Biology and has personally selected and sold hundreds of thousands of live corals. An avid scuba diver who has explored reef systems around the world, Scott shares practical coral care and husbandry knowledge based on real world reef experience.