Fluorescent corals

It has been known for some time now that some coral species are fluorescent but he reason for that phenomenon only recently was found. Apparently, these fluorescent pigments protect them from excessive solar exposure, acting as "sun screen"!

Anemones, corals and jellyfish
Bubble coral (Plerogyra sinuosa - Euphyliidae)

Finger coral (Sinularia polydactyla - Alcyoniidae)

Galaxy coral (Galaxea fascicularis - Oculinidae)

Grape coral (Euphyllia divisa - Euphyliidae) 

Leather mushroom coral (Sarcophyton sp. - Alcyoniidae)

Moon coral (Favites sp. - Hippolytidae)

Mushroom anemone (Discosoma sp. - Discosomatidae)

Bony fish
Blue chromis (Chromis cyanea - Pomacentridae)

Blue streak cleaner wrasse (Labroides dimidiatus - Labridae)

Copperband butterflyfish, beaked butterflyfish, beaked coralfish (Chelmon rostratus - Chaetodontidae)

Sailfin tang, sailfin surgeonfish, ringed tang (Zebrasoma veliferum - Acanthuridae)