What's this on tank glass?

[Allybobo]

Hi guys, I suddenly found some small creatures on my tank glass and they are eating like a snail (but without shell). What are these? Should I keep them or eliminate them?

 

[Allybobo]

It is eating the copepods on glass

 

[TheBear78]

My money is on it being a Flatworm.
There are mixed opinions on their desirability in a reef tank but hopefully someone else can chime in.

 

[Allybobo]

I found similar pictures and this seems to be "ghost flatworm" (Amphiscolops sp.). It's said to be reef safe so I'll keep them there. They look cute.

Hitchhiker Identification Guide

Motile (moves around) Acoel Flatworms (Rust-Brown Flatworm) Photo Credit: @Jessican Reef Safe: No Diet: Photosynthesis and Copepods; While non-parasitic their numbers can get out of hand. Amphiscolops sp. (Ghost Flatworms) Photo Credit: @jstephens1 Reef Safe: Yes Diet: Copepods...

humble.fish

​