Sexing My Killifish.

[rockerBOO]

I recently got 2 Aplocheilus Lineatus killifish and I am unsure if they are male or female. One of them today got a dark line horizontally across their body.

They look a lot like this

http/www.fishandtips.com/database/pictures/00026b2.jpg

But not as defined red on the tips of their tail.

Any idea how to sex them. Also it seems that the "stripped" one is becoming aggressive.

Unaggressive one

Aggressive one

 

[rockerBOO]

Photos added.

 

[InaneCathode]

I bet the top one is a female, and the bottom one is a male.

Claspers are a dead giveaway.

 

[rockerBOO]

I went and returned the aggressive one as he was to persistant, and even though my tank is heavly planted, there is not enough room for them to hide.

Though when i went back after reading up on them, noticed the differences in the male and female, at least from what i could see. The males are brightly colored. and the females are lightly colored. But then there were the "vertical lines" on the back of the fish, which i forget exactly which that is for (male/female)

 

[BigC]

The golden form is a great deal more difficult than sexing the normal wild variety
Males are more colourful and are slightly larger. Females do not have the same yellow colouration in the fins.The back end of the anal fin is pointed in males and more rounded in females.
We killifish fanatics usually carry a torch/flashlight. If you bag the fish in question and hold it up to a light (in this case a torch) in the female you will see eggs in the abdominal area. In your case the fish might be too young but its worth a try.
Regards
BigC