So I've noticed that as of late, my ghost shrimp have been disappearing. Which of the following do you think would be the culprit(s)? Betta, ghost catfish, peacock eel, polypterpus senegalus, or pleco. All are under 6". Please only guess if you have knowledge of these fish.
I think I know, but I want to get your opinion. If it matters, they are in a 20g tank.

inb4: It's too small. Yeah, I know, but not at the moment, I will get a larger one when they get larger.