Home > Ask Our Experts > Why Are My Fish Acting Aggressively?

Why Are My Fish Acting Aggressively?

By: Jennie Kermode - Updated: 26 Sep 2012 | comments*Discuss
 
Neon Tetra Tetras Aggression Aggressive

Q.

We have had our first aquarium for a few weeks now. We started off with 5 glowlight tetras, then waited a week, done a 10% water change as we were told to do. After doing research and going by advise we received from the attendant in the fish shop, we added 6 Neon Tetras and 2 Leopard catfish. All seemed well at first,but now the glowlights are all sitting at the bottom back corner of the tank while the Neons have taken over the front of the tank. The Neons appear to be hearding the Glowlights back into the corner if they do move?

(Miss Sara W, 9 September 2008)

A.

Aggressive behaviour is very rare in neon tetra, but there could be several reasons why it's happening. You'll have to do some experimenting to see if you can find a solution.

Firstly, fish will be aggressive toward other fish who are ill. Your glowlights have probably been together long enough to form a shoal, so it needn't be the case that all of them are ill - if their leader is, they'll all follow when he or she is driven into the corner. Check them carefully for signs of disease and try adding a mild anti-disease agent such as Liquisil General Tonic. If your glowlights are ill, this will give their immune systems a better chance to fight back. It will also make them less vulnerable to illnesses trying to take advantage of their stress at being bullied.

It's possible that, since you're new to aquarium keeping, you've got your water temperature slightly higher than optimum. Try decreasing it very slowly, and watch what happens. Higher temperatures can make normally placid fish more aggressive.

Are your neons bullying each other at all? You may have a mostly male group, in which individuals are competing for status be demonstrating their aggression in front of (or toward) one another. Adding more females can help in this situation. As a rule, larger shoals are more peaceful anyway.

Unfortunately, it is possible that you just have a bad tempered individual among your neons. When this happens it is usually just one, though the others may follow that fish's lead. It may have taken this fish a while to assert itself because your aquarium was a strange place at first. In this case, all you can really do is to watch closely, identify the culprit, and take it back to the shop.

In the meantime, try rearranging the rocks, ornaments and plants in your aquarium. This will make it seem like a strange place and will make the currently dominant fish less confident. Try to create a variety of hiding places so your glowlights can get around more easily. Take care to ensure that they get enough food, as the last thing you need are extra problems caused by starvation.

Good luck! And don't despair - it sounds as if you're handling most things well. The chances are you've just been unlucky.

You might also like...
Share Your Story, Join the Discussion or Seek Advice..
Why not be the first to leave a comment for discussion, ask for advice or share your story...

If you'd like to ask a question one of our experts (workload permitting) or a helpful reader hopefully can help you... We also love comments and interesting stories

Title:
(never shown)
Firstname:
(never shown)
Surname:
(never shown)
Email:
(never shown)
Nickname:
(shown)
Comment:
Validate:
Enter word:
Topics
Latest Comments
  • paris
    Re: Caring for Baby Fish
    okay i was looking in my tank this morning and found little baby fish I think they were just born maybe like a day or two ago but they are…
    27 May 2019
  • Anna
    Re: Rescue Solutions
    Its rough.. I have a dominant male African Cichlid giving me alot of grief. He was in a 55 gal tank attacking everyone so everybody started hiding…
    1 April 2019
  • Madi
    Re: Why do my Fish Keep Dying?
    I got 10-12 fish and traveled 2-3 hours with them in the bag they come with, the sales person said it would be fine Over 4 days they…
    21 December 2018
  • Chocxo
    Re: Should I Keep My Aquarium Lights On?
    I purchased a Betta Fish last month. He is in a 5-gallon tank. The temperature of his water is between 74-78 degrees F.…
    30 September 2018
  • RiN
    Re: Dealing with Bullying Between Fish
    @1KoolCid1 - sounds like it is being attacked. I'd separate them.
    7 August 2018
  • 1KoolCid1
    Re: Dealing with Bullying Between Fish
    My red scat keeps continuing to bite and nip at my Archerfish. I have recentaly gotten a baby green scat that stays near…
    4 August 2018
  • Sid
    Re: Piranhas
    How do you tell the difference between male and female piranhas
    18 July 2018
  • Fishlife
    Re: Dealing with Bullying Between Fish
    If they are the same fish and one of the fins look eatin on what do i do? Im getting nervous because i nevee see them…
    20 May 2018
  • Fishyowner
    Re: Caring for Baby Fish
    Is it ok to put a tiny adult fish in with a baby fish?
    5 April 2018
  • Tee
    Re: Why do my Fish Keep Dying?
    Can 3 female platies, 5 female neon tetras, and a nerite snail live together as tank mates in a 10 gallon take and all be safe?
    26 March 2018