Good sized bristle.

[George03]

Was moving some sand and he scooted away.

 

[mcarroll]

Nice!

Make sure you aren't wasting food in the tank....that's what grows em like crazy. (And they are what keeps the tank from being polluted by that food waste.)

If you're broadcast feeding, stop doing that.

When feeding your fish, make sure you only put as much food in the tank at one time as they can COMPLETELY consume before it gets down into the sand, rocks and filters.

 

[rayadog]

Could that be a fireworm? Just curious, not sure on scale

 

[Baldyreef]

Could that be a fireworm? Just curious, not sure on scale

sort of hard to tell by OP's pic but definitely looks like it could be

 

[anarvaez]

Doesn’t look like a firework to me. I may be mistaken but don’t fireworks have tentacles at the head?

 

[rayadog]

Eh I think I’m wrong to assume that. I think the setae would be more clustered. Fat worm though!

 

[exnisstech]

Fat worm though!

That's a skinny little thing