We introduced some clown loaches to our tank when it was first starting out, they gave it aids...officially referred to now as “THE PLAGUE”. Killed our Bolla sharks, purple sharks, some of the barbs, mini glow fish, and all the loaches...Thanks!
Stephan nailed it. They are catfish. In the other corner are loaches. We have three of them. The largest is about 6" and the other two aren't far behind.