Betta suddenly became aggressive

Discussion in 'Community Tanks' started by rezryk, Aug 5, 2019.

  1. rezryk

    rezryk

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    About 3 weeks ago, I got a male betta for my little 20 gallon community tank comprised of: 10 neon cardinals, 2 kuhli loaches and a siamese algae eater.

    I was told the betta was 6 months old when I got him, it felt good to save the guy from the horrible little cup, filled with brown water, that he was kept in.

    I introduced him to the tank and he seemed fine. I've heard that tetras have a tendency to nip the fins of bettas, but the ones I have just kept their distance and gave the betta a wide berth whenever he got near. My water parameters haven't been absolutely perfect as I had a few issues with my nitrogen cycle, but the parameters weren't dangerous (ammonia never got above 0.2 and nitrates never got above 0.1) and I was doing water changes every 2-3 days.

    Today, the betta started stalking the cardinals and attacked two of them. Both had their fins damaged and couldn't stay upright, I took all three fish out and the tetras died after a few hours. I don't want to return the betta back to the store as they'll likely put him back in a cup, luckily, I've got a spare 10 gallon and once I find a place to put it, he'll go in there.

    I'm trying to figure out what brought about this sudden aggression?
    Did his adult personality and aggression come out after maturing?
    Was he sick? (doesn't seem likely, his colours were vibrant, he ate well, wasn't swimming strangely).

    Either way, I have to find a new feature fish for my 20 gallon, I was thinking an angelfish.

    Cheers
     
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  3. Kiaan26

    Kiaan26

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    What colour is the betta and can you post a picture of your tank?
     
  4. Saibot

    Saibot

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    Very possible that he was sussing out the tank and has now decided to show dominance. Bettas are weird, I have a male who is so chilled the Tetra's bully him, in another tank i have an aggressive female who won't join the other 4 in a sorority. Varying personalities and aggression levels from what I have experienced.
     
  5. OP
    rezryk

    rezryk

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    He's all white, I'm keeping him in a temporary container for now, I'll be putting him in his own tank tomorrow.

    I forgot to mention, I did some pretty heavy trimming a few days ago, foreground plants were dying and back plants were getting extremely leggy and overgrown (weak LED) so I trimmed before putting in a new LED.
    Perhaps the trimmings made him feel more exposed and/or in a new environment. He's had those black marks under his gills since I got him, I figured it's the result of coming from bad water at the shop and would recover over time.

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  6. Kiaan26

    Kiaan26

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    Most likely the trimming was enough of a change to make tank seem like a new environment. So the betta was establishing dominance and his territory. Also the plants probably provided more visual blocks. I've had my betta with 4 white clouds and a big rock in the centre of the tank as a visual block.
     
  7. T. Guppy

    T. Guppy

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    Maybe he was still shy of his new home and was only now starting to get comfortable in his new home and his natural agression came out as a result of getting comfortable..
    I agree with Saibot that they have personalities and levels of agressions. They considered one of the smartest fish so it makes sense that they're all different in that sense. I also have a Betta, and he seems super chilled as well, to the point where the Siamese algae eaters harassed him and his colours started fading, so i moved the SAEs to my other tank and now Tonto the Betta is happy and colourful again. I've recently put 4 baby corys in the tank with him and everyone was worried he'd eat them, and yet the babies are still swimming around happily and he doesn't bother him.
     
  8. OP
    rezryk

    rezryk

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    He's terribly smart. I can stand 1m away from the aquarium and shake the Beta pellet packet and he'll swim to the surface, waiting for the food. There's always a chance a Beta wont intergrate into a community aquarium, but it just makes it that much more satisfying when you pull it off. At least I get another chance to scape an aquarium for him. Only problem, the aquarium won't have a chance to go through a cycle before he gets introduced.
    I'm going to try and squeeze some water out the sponges of my current tank into the sponges which are going in the beta tank.
     
  9. Kiaan26

    Kiaan26

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    Put some substrate, ornaments or the best would be filter media from the 20 gallon to into the new tank.
     
  10. T. Guppy

    T. Guppy

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    Or maybe while you're setting up the new tank you can just put the filter for that tank into the 20L.. Donno if that would help in any way.

    They learn very quickly! My cory adults went and laid more eggs and I decided i wasn't keen on raising more cory fry, so i figured my Betta would enjoy the eggs, so i picked out some of those eggs to put in his tank and soon he realised there was some yummy food on my finger and instead of waiting for me to stick them to the glass he started nibbling from my finger! I thought it was extremely cute lol.
    Out of all the fish I have, which isn't that many (yet) but still, I feel like I've bonded with him the most
     
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  11. Saibot

    Saibot

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    I'd use a good chunk of that substrate which will help boost the cycle slightly.
    Can you not segregate them with a net/bucket or other something just until the tank is cycled.
     
  12. Toy

    Toy

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    Add a temporary perspex divider (with few holes for water flow) in the current tank, setup new tank and setup in series with current tank. Use a cheap powerhead and pvc bell-syphon between tanks to accelerate the cycling of the new tank.
     
  13. Barry Roux

    Barry Roux

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    Maybe an stupid idea but add an small mirror in the current tank so he will be occupied by fighting himself. It use to work back in the day.
     
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  14. OP
    rezryk

    rezryk

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    I think that's the best option.
     
  15. fux940510

    fux940510

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    I've noticed a similar thing with my betta - he was very peaceful and usually kept to himself. This lasted about 4 months. He has grown a little and his colours and tail have developed really nicely, but is now attacking everything that doesn't get out of his way. I think it's down to reaching maturity
     
  16. MariaS

    MariaS Moderator

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    Interesting idea that could well work!!
    Hahha, I could try that on a crazy Oscar!!
     
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  17. MariaS

    MariaS Moderator

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  18. Saibot

    Saibot

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    Fixed it for you ;-)
     
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