ID this pest

[Dovetails]

What are these things crawling on the glass. Looks like some kind of slug.

 

[Fish Styx]

Hard to see with the lighting and without anything for size reference, but looks kinda like a flatworm to me.

 

[ReefHog10]

Hard to tell from pic. Does it look like a snail with no shell? Stomatella snails look kinda “slug-like”

 

[Fish Styx]

I don't think stomatella. While you're right that they do look slug-like, if the two "protrusions" on the front (?) are antennae, the "shell" would be set too far back. I agree it is really hard to make an ID with the lighting.

 

[Dovetails]

Hard to tell from pic. Does it look like a snail with no shell? Stomatella snails look kinda “slug-like”

Yeah. They are clear and look like little ghosts on the glass. The round part is the head and the split part is the tail.

 

[Fish Styx]

Okay, then given the image and your description, it is definitely a flatworm. Most likely an Acoel (based on the "clear" adjective. They are clear/white) No need to panick, as they aren't harmful to your livestock. However, their numbers can reach epidemic proportions, so eradication may be in your best interest. Perhaps consider adding a wrasse to your system, if possible. It will aid in control.

 

[EeyoreIsMySpiritAnimal]

Yeah. They are clear and look like little ghosts on the glass. The round part is the head and the split part is the tail.

Flatworms