Males usually loose their stripes wheras efemales tend to keep them longer and sometimes throughout life. My female does not have stripes so that is not always a good way to sex them. The best way to sex them is round or pointed fins and females will usually have a vent tube slightly visible alll the time.
Rounded or pointed fins is never a reliable way to sex a fish, IMO. As a male can have rounded fins from being picked on by other fishes. And females can have long pointed fins from being kept in good conditions and no fin nipping.
I dont believe that you can sex a jag by the shape of its fins. I have seen some huge beautiful males with rounded fins. I have seen some big females with real long pointed fins. It all depends on the fish
My jag doesnt get nipped on at all I kind of had some good luck when buying agressive fish, they are all pretty calm no one really bothers anyone, I guess cuz there small now and have so much room to swim. My biggest fish is my silver arro and he's only about 8 or 9 inches. Thanx for all the input fellas. Since im getting mixed answers im gonna wait till it gets bigger and post pics then.