You did the right thing. E cats are pugnacious and highly territorial towards conspecifics. That aggression begins fairly early out of the fry stage and increases towards adulthood.
Hey, good to see you Oddball! Hey, I picked out the cat that didn't look like the others. He doesn't have the dark caudal stripe and his head was flatter, broader and he is more purple than red. Think he might be something besides m. electricus? Want some pics?
Wait til he's settled down and eating. Pics will be easier to decipher when the cat isn't displaying stress colors. It's likely to still be Malapterurus electricus since this species is propagated as a food fish and, therefore, more available as juvies in the hobby.
Still, will compare the pic to all 16 known species.
You did the right thing. After they get a little older they do become more and more territorial. Electric cats are my favorite. As if you could not tell. Will be waiting for some pics of this guy. When he is ready. And welcome to the Ecat family.
Propagated as a food? Must be prolific spawners, then. I'll try to find out if the supplier got them from a farm or the wild. Here are a few sloppy shots, but they have visible fin ray counts in them! This little guy is on the move and doesn't want to sit still at all so all shots are moving shots in low lighting. AKA, they could be worse. That's sand and bubbles, not ich. He was clean as a whistle when he went in.