That's a boy. Look at the longer anal fin...that's the giveaway. Also, a beard if he's got one. You got this fish from titolatino, right? I just went through this with a fish from him as well. The anal fin is the only way to tell for a while. The girls in this batch have small, rectangular anal fins with no length to them. I had to do an emergency isolate on my girl-really-a-boy because he was starting to fight with his sisters, and they were ripping his fins.
I'd isolate and go from there. I'll bet his fins will develop nicely once he's on his own, and you'll get the confirmation you need. It seems like these giants are quite unique...a lot of conventional sexing techniques just don't work, and you can't tell until later.
Last edited by bethyMT; 01-17-2013 at 10:52 AM.