Here's a Herotilapia multispinossa (rainbow cichlid) to compare
They usually top out at no more than about 7".
Below a young melanurus (the species name synspillum name is no longer valid) This is because it was discovered thru DNA testing that melanurus, and synspilla are the same species, simply color variants.
And because the name melanurus was used first, (back in 1862) and the name synspilla not used until 1935, synspilla(um) becomes invalid.
Here is a young melanurus (younger than theOPs photo, these get to about 16".