Good looking fish. Im wondering what he is myself. What size is he?
He's definatly not a Lithobate, there's no spots, body shape is not right, and the lateral stripes are to straight and perfect.
I don't think he's a Protomelas spilonotus (Mara Rocks), theres no orange tint on his body, the anal fin is not redish-orange, and the stripe on his head is not thick or long enough. Plus, they are very slow to grow into there colors but that's why I asked his size. I have one M thats 5" and just started getting his blue, about 2 weeks ago. First colors to come in are the orange on the body and the anal fin. his body shape looks dead on, even with that big eye. So I would say some sort of Protomelas spilonotus, maybe a hybrid or maybe he is a young (Mara Rock) that's been juiced and why the coloring is not right.
I'd love to see more pics.