I have just recently acquired a tank and some fish, but I have no idea what one fish is. I can't find a picture that looks the same either.
The fish is a few years old (I don't know exact age, 1-2 years old) and approx 4-6 inches:
The fish is a few years old (I don't know exact age, 1-2 years old) and approx 4-6 inches: