Marine leech or slug?

[lukewod1]

Hey people so I work at Petco and have my own saltwater tank. When cleaning one of the tanks I saw this guy and have no idea what it is kinda looks like a saltwater slug or a marine leech but can’t tell it’s like black or red. Anyone know what it could be?

 

[EeyoreIsMySpiritAnimal]

Sea cucumber?

@ISpeakForTheSeas

 

[ISpeakForTheSeas]

Assuming it's round, a cuke would be my first thought, though I'm struggling to tell much from the pics at the moment - OP, any chance of closer up pics under brighter, white light?

Is it round like a tube, or is it flat/flattened? Can you describe the texture?

 

[JGT]

Looks like a turd so think cuke is the right call.