This thing is a bristle worm—or possibly a eunice worm
A man got a shock when he discovered a 3-foot-long bristle worm that went hiding in his fish tank for two years.
He said it was possibly a eunice worm (Eunice aphroditois), known as the Bobbit worm. It was uncovered when the man cleaned his tank.
“It’s huge!” he said. “I can’t believe I haven’t seen it before! Two years!”
The uploader later wrote: “I was breaking down the tank (as I was moving it), hence it looking shoddy.” He added that he only noticed the worm “because I had whole coral colonies missing after a single evening.”
Eunicids, found in warmer oceans across the world, can get to nearly 10 feet in length.
They’re also known for their incredibly fast attack speeds and nightmarish looks: