Looks like a delta.
Did you add him to the community tank without quarantining him? Not to alarm you but that's probably not the best idea since you don't know if he could possibly be carrying some illness. I foolishly added a new fish to my sorority after only a week of QT and lost all but one of my females and half my neon tetras to columnaris. They went from healthy to dead in less than 12 hours. Probably $100 or more worth of breeder females... lost.
Whenever you add a new fish to a community tank it should be QT'd for at least 2 weeks, preferably a month.
*Be smart.. Do your research!!*