It's a male carpintis. 99.9% sure. It has an odd shape to it, what size tank do you have it in? What size tank was it in when you purchased it and how long was it there?
It's too green and pearly to be cyanoguttatus.
The lack of a black dot on the dorsal, slenderness of the fish, and the slight fin-extensions all indicate male. You can't see its tube in the picture, but males have a pointed tube and females a rounded.
A black dot on the dorsl indicates female. Why do you think most cichlids with black in the dorsal are females? My male festae, carpintis, managuense, motaguense, and severum ALL have black in the dorsal fin...