Neon Bicolor Open Brain Coral (Trachyphyllia geoffroyi)

Open brain corals are free-living — no attachment point, just a single fleshy polyp resting loose on the sand, which means it can be nudged into a better spot without hurting it. During the day it deflates down into a modest ridged mound, then at night it inflates to several times that volume as it extends feeding tentacles and hunts, a transformation dramatic enough that new reefers sometimes think something's wrong. This one splits color cleanly down the ridgelines in two tones, which shows up best right after that nighttime inflation.

Care level: Easy · Light/Flow/Placement: Low-moderate light, low flow, sand bed · Max size: 4-6" · Diet: Photosynthetic, benefits from regular meaty feeding