Flat worm? Sea slug?

[Jaden9933]

just finished gluing down 14 new frags only to realize I forgot to dip them all and I found this on the side of the bucket. What is it?

 

[Jaden9933]

Slug?

 

[Townes_Van_Camp]

Not a flat worm.

 

[Jaden9933]

Not a flat worm.

Figured it was too big but I didn’t wanna rule anything out. Thank you!

 

[Goaway]

Some flatworms get rather large. Could be. It's curled up so I can't tell. If it was flat, it's probably a planarian flatworm.