Maedhros (the catfish) grabbed the rock cave right away and quickly established himself as the boss of the tank.

Why does this not surprise me? :P

The cichlids--such curious, adorable little fish--would poke their little noses into the cave, Maedhros would come flying out, and they'd poke no more.

I'm sure it's your fault for naming him that. Now I keep thinking of the Dagor Bragollach. "...and the orcs fled before his face."

Your Mack sounds adorable (I can never tell fish apart, especially not fish of the same species).