| Firemouths are tough to sex as both males and females can have the same traits. Some say go by color as male will have brighter colors, but females will also color up just as nicely as males. Fin shape can also be misleading as some females will show longer fins that you would expect to be a male.
These fish also appear to be pretty small give them some time. The best way to get a pair is to purchase 6 fish at a small size like they are here and let them pair off. For some people that is where the biggest problem lies as they do not have the room for 6 fish or anywhere to take the other fish to once you get the pair you want.
Once they get a bit bigger you can vent them as that would be the best and most accurate way to sex them.
A great fish by the way, good luck with them.
Brian | 
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