Male or female Firemouth?

[Ave]

There baby firemouths in our local LFS and I would like to have a pair. But they are very small - ca 3 cm. How early is it possible to distinguish males from females?

 

[Nolapete]

As with most central/south american cichlids, the dorsal fin is the most used and usually accurate way of determining sex early. The males will have elongated, pointy, arrow-shaped dorsal fins and the females will have more rounded or squared-off dorsal fins. Exclude any streaming points on the tips of the dorsal when using this method as both males and females in good condition may have streaming points. Use about 90-95% of the dorsal fin from body to tip to make the determination.