Thanks everyone! I am just totally over the moon with this guy. I've decided to name him Wraith because his flowy black fins reminded me of JRR Tolkien's Nazgul. He doesn't have the personality of the Nazgul though... He's very skittish. I tried for ages to get him to flare using mirrors and another male and it was a no go. Ah well, I'll try again later.
Abby - I think you're right in calling him a black orchid.
jiayaw - I'm actually from Hamilton, Ontario and I got him from the Hamilton Big Al's. Most of the other bettas there were... not the best. They did have a nice pure white halfmoon (I think) though.
And newfiedragon -