Unknown hitchhiker?

looks like a zoo eating nudibranch. not sure though.

It's definitely a nudibranch of some kind. Keep an eye on it, because it may or may not be beneficial. A picture of it from above that shows its whole length would help people give you a more specific ID.

nudi, best just get rid of it yet i have three lol

The picture looks stretched until you click on it and enlarge it.

The creature died the next day. It was pretty though.