Why is my Open Brain Coral receding and showing its skeleton?

Tissue recession usually stems from physical damage, such as being placed on sharp rocks, experiencing flow that is too strong, or suffering from unstable alkalinity and calcium levels. Ensure it is placed exclusively on a soft sand bed with gentle, indirect flow.

Can I place my Trachyphyllia on the rockwork?

No, it is highly recommended to place them only on the sand bed. Their fleshy tissue expands significantly during the day and will easily tear against sharp rocks, which often leads to lethal bacterial infections.

How often should I feed my Open Brain Coral?

Target feeding one to two times a week with meaty foods like mysis shrimp or LPS coral pellets is ideal. Turn off the flow temporarily and gently place the food near its mouth when its clear tentacles are extended.

Why is my coral's mouth gaping open?

A gaping mouth can be a sign of stress from poor water quality, sudden parameter swings, or a reaction to being harassed by fish or invertebrates. If it persists, test your water parameters immediately and observe the tank for potential nippers.

Why does my Open Brain Coral shrink during the night?

It is entirely normal for this coral to deflate its fleshy mantle after the lights go out. During this time, it typically extends small, clear feeding tentacles around its mouth to capture passing zooplankton.

MarineCoralsIntermediate

Open Brain Coral

Trachyphyllia geoffroyi

The Open Brain Coral is a spectacular, fleshy large polyp stony (LPS) coral treasured for its vibrant fluorescence and signature folded appearance, making it a stunning centrepiece for the marine sand bed.

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Ideal Conditions

Temperature: 24 – 27 °C
pH range: 8.1 – 8.4
Hardness: 8 – 12 dGH
Salinity: 1.024 – 1.026 SG
Adult size: 10 – 20 cm
100L+: 100 litres+
Lifespan: 10 – 50 years
Diet: Photosynthetic and carnivorous
Water flow: Low to moderate
Preferred setup: Mature reef with an accessible soft sand bed

About the Open Brain Coral

Trachyphyllia geoffroyi, commonly known as the Open Brain Coral, is a large polyp stony (LPS) coral that boasts some of the most intense fluorescent colours in the marine hobby. Featuring a deeply lobed, fleshy mantle that expands beautifully over its skeletal base, it typically adopts a figure-eight or fluted circular shape. These corals are primarily solitary, forming unattached, free-living colonies in their mature state. Their striking appearance and relative hardiness have made them enduringly popular among intermediate reef keepers. While peaceful, they do possess short sweeper tentacles and require adequate spacing from neighbouring corals.

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Is it right for your tank?

Check Open Brain Coral against a habitat you already keep. We compare water type, temperature, pH, adult size, group needs and everything living there.

Where Open Brain Coral comes from

Native range

Indo-Pacific, Red Sea, Great Barrier Reef

Countries / regions

Australia, Indonesia, Philippines, Fiji, Egypt

Habitat

Reef slopes, sheltered lagoons, and sandy or muddy seabeds subject to gentle tidal currents.

Similar species

Lobo Brain Coral
Lobophyllia spp.
Meat Coral
Acanthophyllia deshayesiana
Scoly Coral
Homophyllia australis

We’re adding more full species guides as the catalogue grows.

Compatible tank mates

Reviewed guidance based on this species' recorded traits.

View all compatibility

Banggai Cardinalfish
Pterapogon kauderni
Peaceful, mid-water swimmers that will not bother or compete with bottom-dwelling corals.
Great
Firefish
Nemateleotris magnifica
Gentle dartfish that pose absolutely no threat to fleshy LPS corals and add active colour above the sand bed.
Great
Banded Trochus Snail
Trochus radiatus
Excellent cleanup crew members that will safely graze algae around the coral without damaging its soft tissue.
Great
Coral Beauty Angelfish
Centropyge bispinosa
Like many dwarf angelfish, they carry a persistent risk of nipping at fleshy LPS corals, which can cause the coral to remain retracted and slowly decline.
Compatible with caution
Ocellaris Clownfish
Amphiprion ocellaris
May attempt to adopt the large fleshy coral as a surrogate anemone; their rigorous rubbing can irritate and eventually damage the delicate tissue.
Compatible with caution
Raccoon Butterflyfish
Chaetodon lunula
A corallivorous fish that will actively graze on and quickly consume the fleshy mantle of the brain coral.
Not recommended
Niger Triggerfish
Odonus niger
A highly destructive, large predator that can easily bite through the coral's skeleton and destroy the animal.
Not recommended

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