It's addictive isn't it?
Yes that's an "electric yellow" or "yellow lab" which ever you want to call it I have heard them called "yellow prince" too. Both those fish are African Cichlids and both are aggressive. When they start fighting my money is on the Blue Johanni so long as he doesn't eat the yellow lab then maybe nobody wins. The yellow labs are poisonous when eaten. It shouldn't the Blue Johanni that I had would just roll the other fish over and chew out enough of the guts to where it was a fatal injury and then left them for dead.
The blue was is already a bastard. He's been chasing the yellow around all night, even though the yellow is minding it's own business.
I knew they are very aggressive, but I thought they could live together?
Hell, they were in the same tank when I got them.