What is this slug thing?

[Xarria]

I’ve found a few of these black, speckled slug looking things in my sump and I cannot figure out what they are despite searching the internet quite a bit.
They don’t appear to have a shell and are about 1/2 of an inch long. It doesn’t look like it has a shell, so I don’t think it’s a stomatella or other snail.
Here’s a video of it moving around.

 

[WheatToast]

Possibly a Bulla bubble snail or related gastropod. These are said to feed on diatoms, cyanobacteria, and beneficial microfauna, so I would be cautious of keeping them.
https://floridapets.com/Bubble-Snails-6
https://www.reef2reef.com/threads/bubble-shell-snails.548839/

 

[Xarria]

The bubble snail is definitely the closest looking thing I’ve seen so far! The color is a bit different but the body shape appears to be very similar.