If it's a Lake Malawi tank, the horizontal stripes suggest a Melanochromis sprecies and the blue sheen is the sign of a male - but I can't go further than that.
@Ebirah766 You might be right, but I would want to see the pelvic fins properly to be convinced. I was also puzzled by the barred fish in the background - might it be Coelotilapia joka?
