When to jar your betta fries?
First time betta fish breeders is always questioning about when to jar your betta fries. Base on experience of my friends below are a few tips for jarring betta fishes.

Jarring can start from 2nd month onward. Fish length is around 3cm.
If you breed your fishes in a large container like a pond, you wait till 3-4 months before jarring. Fish also grows faster in a large enclosure.
Some breeder jar as early as possible to train their betta fish to be aggressive and this allows them to cull betta fries early.
Referring to my first Dumbo betta spawn, I jarred the betta fries after 2 month 1 week from the day they hatch.
More plants in the out grow tank will help reduce aggression and fin bitting.
Jar as soon as you see aggression to minimize fins biting.

For Singaporeans wondering where I get my jarring cups from, I got them from SKP. I bought 50 clear cups for around $5-6. This cups are slight more expensive as they are more rigid and clearer. Product code is “CUP-PET-12”

For thoses that have a bigger pocket, you can op for cny goodies container from liang teck plastic, they cost around $0.80-$1 per piece. They are also the supplier for the infamous SU 830 container that is frequently used by betta fish hobbyist for fish keeping.

Jar your betta fries summary
Separation of betta fry should begin from the second month onwards, with a size of approximately 3 centimeters. If raised in a large pond, they should be separated when they are 3–4 months old, as they grow faster in a large area. Separating fish early helps train them to be aggressive and facilitates selection. However, signs of aggression should be observed in order to separate them immediately, reducing the problem of fin biting. Adding plants to the tank can help reduce aggression and fin biting.