It looks like a young male to me. Look behind the stomach, and see if you can see the egg sac. It will be a yellowish color. On the picture you posted, is a small circle behind it's stomach. Looks like a reflection in the glass.This is where the egg sac would be located. Most females start showing the oviposter at 3-4 months old, but some males have it as well. I have had more than one (female) turn out to be a slow developing male. The reason I think it is a young male, is because of the length of the caudal. I raised a orange spawn, and am used to looking at them. He looks to be about 3 months old. The dorsal is thin and the anal looks long. Only time will tell for sure, but it should start developing really fast at this stage.