Black Ghost Knifefish
These guys are really cute, but knifefish shouldn’t be kept inc lose proximity like this. I assume/hope this is a sale tank. They generate weak electrical impulses, almost like electric eels, to figure out the world around them and look for prey. When you have multiples, the signals clash against them and stress them out.
That aside, they’re amazingly mobile. They can move in almost any direction. Watch.
(Source: https://www.instagram.com/)