Marine Life & Conservation
Hard and soft corals explained: what you're looking at on the reef
A coral is a colony of tiny animals called polyps — sometimes hundreds of thousands of them. Reef-building hard (stony) corals have six-fold symmetry and live with algae called zooxanthellae, which feed them through photosynthesis; soft corals have eight tentacles per polyp and bend with the current. When stressed, corals expel their algae and turn white: bleaching.
By 71 Guardians · Published 29 Oct 2026
What is a coral polyp?
Almost all corals are colonies of many individual animals called polyps. Each polyp has a mouth ringed by tentacles; in hard corals, the polyps build a limestone skeleton, layer by layer, that becomes the reef.
What's the difference between hard and soft corals?
- Hard (stony) corals: polyps with six tentacles or multiples of six (hexacorals), building the rocky reef — table, brain and plate corals.
- Soft corals: polyps with eight tentacles (octocorals), flexible and often colourful — common on Red Sea walls.
What do zooxanthellae do?
These algae live inside the coral's tissue. The coral gives them shelter and the carbon dioxide they need; they feed the coral with the products of photosynthesis. When the coral is stressed — by heat, for example — it expels them and turns stark white. That is coral bleaching.
How can you avoid damaging corals?
- Don't touch, stand on or kick the reef — polyps are living tissue.
- Keep good buoyancy and tuck in gauges and straps.
- Choose a reef-safe sunscreen or cover up with a rash vest.
Frequently asked questions
Are corals plants or animals?
Animals — colonies of polyps — that live in partnership with algae.
Why do corals turn white?
Stressed corals expel their zooxanthellae algae and lose their colour; this is bleaching.
Can I touch soft coral?
No. Touching any coral damages living tissue, and it's prohibited in Egypt's protected areas.
Questions before you dive with us?
Message our team on WhatsApp — we're divers in Hurghada and happy to help.
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- Coral Reefs — hard and soft corals — NOAA Florida Keys National Marine Sanctuary
- Corals: zooxanthellae — what's that? — NOAA Ocean Service Education