I know that betta fish can be aggressive towards other fish, especialyl brightly coloured ones. What I'm trying to figure out is if this is nature or nurture, if that makes sense...

I have an existing tank with 5 male endlers - all bright coloured - and a couple of snails, and 8-10 shrimp. Lots of plants. I just got a new baby betta fish.


If I put the baby betta in there, would it start out aggressive towards the other fish, or - since it's growing up with them - would it be ok?

1 Answer 1


Individual bettas are unique, so you should keep an eye on him on the first days anyway. You never know.

Typically, a baby will not be aggressive, I have seen many very small bettas kept in community tanks with a lot of different fish.

Additionally, if you add the betta while other fish are already present before, the betta will not feel that it's HIS territory and that he should defend it, so that will help too.

And because he will grow up with them, as you said, he might stay peaceful.

However, it's very possible that, growing up, becoming bigger, he will one day become aggressive and attack the other fishes and dominate them, especially colorful ones. So to answer your question, they are aggressive by nature, they don't need to be taught that. They see another fish that looks like them and they want to prove that they are bigger and stronger.

Your setup and idea sound very safe. How big is the tank?

Edit: Be aware that bettas can also be the victims of aggression. They are slow moving and have long, flowing, tasty-looking fins. Make sure the baby betta is not being bullied by faster fish.

According to my experience: The snails will be no problem, but the shrimps may be eaten by the betta eventually.

I'm pretty sure you will have to separate the betta from the endlers and shrimps when he will be bigger, so prepare for that.

  • Thanks @Manuki! The tank is 10 gallons, so not small but not large either. The endlers are all small (about an inch each), so space would not be an issue, but I may keep it separate anyway. I didn't think about the other fish being aggressive towards the betta...
    – Sagar
    Commented Aug 21, 2019 at 15:49
  • @Sagar how young is the baby anyway ?
    – Manuki
    Commented Aug 21, 2019 at 16:00
  • Bought it from a store - it's about 1/2 an inch long, but doesn't say how old.
    – Sagar
    Commented Aug 21, 2019 at 17:55
  • 2
    @Sagar: according to my little experience, at that size it is very young. My first beta, it lived for several years, and just before its death I showed it to a professional. Unfortunately, there was nothing to be done to help, but that guy told be he actually never saw a beta so big. I bought it when it was (most likely) somehow bigger than yours - but I also did not know the age.
    – virolino
    Commented Aug 23, 2019 at 11:05

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