|Small mud snail, smaller green hunter|
He chose one snail after another, and slithered around and around and around each one, looking for a vantage point to pull the snail out of its shell. Only trouble was, he was far too small to manage it.
He wasn't all that hungry; in the photo you can see the dark spots in his belly; undigested food. Another worm, maybe? An unwary amphipod?
I saw him again this afternoon, on the glass wall. He was completely green; all his food had been digested.