Plotosidae (Eeltail catfishes)

There is only species (Plotosus lineatus) in the Eeltail catfish (Plotosidae) genus that lives on the coral reef.
Eeltail catfish are excellent at removing leftover food and dirt from the aquarium.

These fish have poisonous spines by the dorsal and pectoral fins, so care should be taken whith handling. Their poison can be dangerous for humans, especially if one is stung multiple times. 

They have a lovely appearance when young, but are less attractive as adults.
Unless kept in a group, they will remain hidden. 

Eeltail catfish can swallow both fish and invertebrates in one go.