Short Answer
- Count the tentacles around a single open polyp when the photo is sharp enough.
- Goniopora is commonly identified by 24 tentacles per polyp; Alveopora is commonly identified by 12.
- Do not count from blurry, angled, or half-closed photos. The rule is only useful when the polyp is clearly visible.
- Use polyp extension, tip shape, and colony context as supporting evidence, not replacements for a clear count.
The most useful clue is tentacle count
When the coral is fully open and the photo is sharp, count the tentacles around one polyp. Goniopora is commonly described with 24 tentacles, while Alveopora is commonly described with 12.
This is a strong first-pass clue, but it still depends on photo quality. If the polyp is tilted, moving, or partly closed, the count can be misleading.
Goniopora vs Alveopora comparison
| Trait | Goniopora | Alveopora |
|---|---|---|
| Common tentacle count | Often described as 24 tentacles per polyp. | Often described as 12 tentacles per polyp. |
| Polyp impression | Can look denser or more daisy-like when extended. | Can look more open, rounded, or flower-like. |
| Best photo evidence | Sharp close-up of one fully open polyp. | Sharp close-up of one fully open polyp. |
| Common trap | Counting from a moving or angled polyp. | Assuming shorter extension proves Alveopora. |
How to photograph Goniopora or Alveopora for ID
- Turn down flow briefly if safe so the polyps stop whipping around.
- Photograph one fully open polyp straight-on, not only the whole colony.
- Use reduced-blue lighting so the tentacle edges are visible.
- Take a colony-wide photo as context after capturing the close-up.
Keep confidence tied to the evidence
If you cannot count tentacles, avoid a hard ID. A broad flowerpot coral label with a note such as likely Goniopora or likely Alveopora is better than pretending the photo proves more than it does.
This matters because hobby labels can travel with corals long after the original evidence is lost. A careful confidence note keeps the record useful later.
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Sources
References and further reading
FAQ
Frequently asked questions
01How many tentacles does Goniopora have?+
Goniopora polyps are commonly described with 24 tentacles. Use that clue only when a polyp is fully open and the photo is sharp enough to count.
02How many tentacles does Alveopora have?+
Alveopora polyps are commonly described with 12 tentacles, which is why tentacle count is the standard first-pass clue for separating it from Goniopora.
03Can I identify Goniopora vs Alveopora from a whole-colony photo?+
Sometimes, but a whole-colony photo is often not enough. A sharp close-up of one fully open polyp is much more useful.
04Should I rely only on tentacle count?+
Tentacle count is the strongest simple clue, but photo quality matters. Use extension pattern, polyp clarity, and repeated observation as supporting evidence.