© Eva DiDonato/NPS / Public domainGoniastrea Retiformis
Goniastrea retiformis is a reef-building coral in the brain coral family, known for its small polygonal corallites that pack tightly together, sharing walls in a honeycomb-like pattern. Called the lesser star coral in English, it is widespread across shallow reef flats in the Indo-Pacific, where it withstands intense light and strong wave action. That resilience makes it one of the more forgiving corals for beginners. Colonies grow to tens of centimeters across, and the dense, geometric arrangement of polyps gives it a quietly striking texture rather than flashy color, making it a good pick for anyone drawn to understated, architectural beauty in a reef tank.
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Goniastrea Retiformis key facts
- Care level
- Beginner-friendly
- Size
- Colonies to several tens of cm
- Temperature
- 24〜27℃
- Diet
- Mainly nutrition from symbiotic zooxanthellae, supplemented with meaty coral foods offered at night.
- Lighting
- A reef-flat species that tolerates moderate to fairly strong light, but reduce the light for newly added colonies and raise it over several weeks.
- Flow & Placement
- Medium flow. It can sit anywhere from the sand bed to mid-height, but leave space, because tissue recedes where the skeleton edge touches a neighbouring coral.
- Water Temperature & Quality
- Water 24-26C, specific gravity 1.023-1.025, salinity 33-35 ppt, KH 8-12. It consumes calcium and magnesium, so test and replenish them regularly.
- Feeding
- Most of its nutrition comes from its zooxanthellae. The corallites are small and cannot take large items, so feed powdered or finely particulate coral food after lights-out.
- Notes
- Growth is slow, and tissue recedes readily after sudden water-chemistry swings or prolonged high temperatures. As a scleractinian it is on CITES Appendix II and international trade requires permits.
About Goniastrea Retiformis
Goniastrea retiformis is a hardy brain coral with tightly packed polygonal corallites, native to shallow Indo-Pacific reefs. It tolerates strong light and current, making it a good choice for beginners.
7 things to know before welcoming a Goniastrea Retiformis
1Bright Light and Flow
Native to shallow reef flats, this species does well under fairly strong lighting and moderate water flow. Placing it in a brighter spot in the tank helps keep it stable.
2Grows Into a Solid Colony
Small corallites share walls and pack tightly to form a solid, encrusting colony. Since colonies can eventually reach tens of centimeters across, it's worth leaving extra room for future growth when placing it.
3Give Neighboring Corals Space
Faviid corals like this one can extend sweeper tentacles at night that irritate neighboring corals. It's best to leave adequate spacing from other corals when planning your layout.
4Hardy, But Dislikes Sudden Change
Although it's considered beginner-friendly and generally hardy, sudden changes in lighting, temperature, or water chemistry can stress it and cause it to pale as it loses zooxanthellae. Adjust its environment gradually rather than all at once.
5Feeding Is Optional
Most of its energy comes from photosynthesis by symbiotic algae, so feeding isn't required to keep it healthy. If you want to support more robust growth, offering fine particulate food while the polyps are open can help.
6Calcium and Mineral Balance Matter
Because it builds a calcium-carbonate skeleton, its growth depends on a healthy balance of calcium, alkalinity (KH), and magnesium. Regular water testing helps you keep these parameters in a good range.
7Acclimate Slowly When Introducing
Corals are sensitive to abrupt changes in water chemistry, so a slow drip acclimation is recommended right after bringing it home. Keeping lighting a bit subdued for a while after placement also gives it time to adjust.
Frequently asked questions about Goniastrea Retiformis
- Q.Is this coral suitable for beginners?
- A.Yes, it's considered a hardy, beginner-friendly species. It tolerates strong light and flow, so basic water quality management is usually enough, though sudden environmental changes should still be avoided.
- Q.How large does it grow?
- A.Colonies can grow to tens of centimeters in diameter. It's a good idea to leave room for this future spread when choosing where to place it.
- Q.Does it need to be fed?
- A.Feeding isn't strictly necessary, since it gets most of its energy from photosynthetic algae. That said, occasional feeding can support better growth.
- Q.Can it be placed close to other corals?
- A.Faviid corals can extend sweeper tentacles at night that irritate nearby corals, so it's best to leave adequate spacing from other corals.
- Q.Is this species restricted under CITES?
- A.Goniastrea Retiformis is listed in CITES Appendix II. International trade requires a permit from the exporting country, but as far as CITES is concerned, no registration is needed to buy or sell individuals already legally in Japan.
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