It looks like a common plec to me as well, but it also looks quite young and its quite hard to tell common and sailfin youth apart when they are little- how many inches long is he? If you can get an above pic looking down on him, it will also make it easier to tell if its a "he" or a "she" but im guessing its a "he" for now .
Hmm....names.....
If its a "he", how about some names like Shadow, Lupin, Anglo, Sagre, Otto...?