My Bristle Worm Found in Two Pieces

[NotSoLocalFishFan]

I’ve had a very large bristle worm (about maybe 40ish or more centimetres?) living in my tank for a while now, they’ve never been a problem and I’ve quite enjoyed their existence but I just looked in my tank and found the poor thing split in half. It’s now in two pieces and I have no idea why it’s like this. Is it like an anemone and both pieces will live? Or is it kicked the bucket and I should remove the pieces. I’ve picked up one of the halves and it seems to like move around for a bit before stopping again, and the other bit is hiding in my rocks and I can’t get it out. Why did this happen? Water quality? Just at the end of its life? Will it be alright? Will both parts live like a split anemone or will just the side with the head survive?

 

[NotSoLocalFishFan]

Okay I managed to like nudge the one half in the rock and it’s reactive while the other half doesn’t seem to be. How can I tell which sides the one with the head? I want to know if it’s the tail that was chopped off and not responsive