Definitely a Frontosa. I've seen dark colored individuals and in some cases black individuals. I'm no Frontosa expert but the dark ones I've seen where usually Mpimbwe or Kitumba. Even rarer is to see a dark colored juvenile, so I'm unsure if some start out like that or that some just develop that coloration when they become a Alpha.
Regardless Frontosa are awesome fish even though their presence on here is nearly non existent there are sites like Cyphos where you can find more info on them as well as vendors who sell juvies and wild caught. They look beastly but are mellow for cichlids. Their biggest drawback is how slow they grow IMO.
