Aggression Or Territorialism In Danios

[alysonpeaches]

My tank is 4 weeks old and I have 7 zebra danios in it. (96 litre tank). I initially had 4 small danios, but I thought one was getting picked on, so I bought 3 more, thinking a larger shoal would be better. The new ones are somewhat larger than the orginal ones. What has happened now is one large danio is patrolling the area in the centre of the tank where the large piece of bogwood covered in java moss is. If any of the other fish enter this zone, he chases them off. (think its a male, but really not sure).

So my plan backfired. What shall I do about this?

 

[Miss Wiggle]

Thing is with any animal while we know the general behaviour trends there will always be variance between individuals and you will occasionally get a rogue animal who does not behave how the book say’s they should. What you should do is prop open a fish book on the danio page in front of the tank so he can read up and see what he’s meant to be doing just kidding

There’s a couple of things to investigate/try which may make things better, however you may find that you are unable to get any improvement, if that’s the case usually if you return the fish to the store you bought it from they’ll take it off your hands.

OK, so firstly the main thing which makes animals behave aggressively or erratically is fear, if an animal is backed into a corner it will often lash out. The three things which are likely to make fish behave like this are poor water quality, inappropriate tankmates or a inappropriate tank environment (wrong size, décor etc).

So firstly, what are your water stats for pH, ammonia, nitrite and nitrate?

Do you have any other fish apart from the danios in the tank, if so then what species, how many and how big are they at the moment?

Can you post a picture of your tank so we can see how much cover or hiding places the danio’s have got?

 

[alysonpeaches]

Thing is with any animal while we know the general behaviour trends there will always be variance between individuals and you will occasionally get a rogue animal who does not behave how the book say’s they should. What you should do is prop open a fish book on the danio page in front of the tank so he can read up and see what he’s meant to be doing just kidding

There’s a couple of things to investigate/try which may make things better, however you may find that you are unable to get any improvement, if that’s the case usually if you return the fish to the store you bought it from they’ll take it off your hands.

OK, so firstly the main thing which makes animals behave aggressively or erratically is fear, if an animal is backed into a corner it will often lash out. The three things which are likely to make fish behave like this are poor water quality, inappropriate tankmates or a inappropriate tank environment (wrong size, décor etc).

So firstly, what are your water stats for pH, ammonia, nitrite and nitrate?

Do you have any other fish apart from the danios in the tank, if so then what species, how many and how big are they at the moment?

Can you post a picture of your tank so we can see how much cover or hiding places the danio’s have got?

Not a brilliant photo I admit.

Ammonia 0, nitrite 1 ppm, not tested nitrate today.
No other species. There are 3 pieces of bogwood which have hidey holes underneath. The other fish are using them of course to get out of the way of the bully. They also hide in the plants: amazon swords mostly.

 

[ox5477]

The dominant male in my shoal of giant danios tends to get nippy with all members of the shoal though I rarely see him actively chase anyone away and keep them from his area.... interesting

Ox

 

[alysonpeaches]

The grey blur in the middle of the picture is the bully. All the others are hiding. They seem particularly ravenous at feeding times but Im only feeding them sparingly because of the nitrites.

 

[Miss Wiggle]

tank looks really good and there's plenty of cover so that's not an issue, no other species so it's not that, but water quality could well be the problem.

what are you doing to get rid of the nitrites? I would suggest waiting before you take any action until the water quality is stable and good, then see how his behaviour is.

Litlle tip to get you through until that point, if you re-arrange the decor in the tank it removes the estbalished territories, basically puts all the fish on a level playing field and can help to dissapate agression.

 

[rhostog]

Very interested to read this thread. One of my 4 zebra danios (a female) is poorly with a swim bladder problem, and the only male zebra is being extremely aggressive towards her. Every time she emerges to try to feed, he chases her back into the plants, pursuing her relentlessly, far more than the usual danio bickering. As I've not been able to catch her, I've resorted to isolating him temporarily to give her a chance to feed, otherwise she just doesn't stand a chance. I guess it makes a sort of sense if he's chasing away a sickly fish which could potentially carry something infectious.

Sorry - I know it doesn't help with your problem - but I'll be interested to hear how you get on.

Your tank looks really good by the way

 

[Miss Wiggle]

Very interested to read this thread. One of my 4 zebra danios (a female) is poorly with a swim bladder problem, and the only male zebra is being extremely aggressive towards her. Every time she emerges to try to feed, he chases her back into the plants, pursuing her relentlessly, far more than the usual danio bickering. As I've not been able to catch her, I've resorted to isolating him temporarily to give her a chance to feed, otherwise she just doesn't stand a chance. I guess it makes a sort of sense if he's chasing away a sickly fish which could potentially carry something infectious.

Sorry - I know it doesn't help with your problem - but I'll be interested to hear how you get on.

Your tank looks really good by the way

you get that quite a lot in any species, sick fish are bullied, it's part of the whole natural selection thing, the stronger animals fight the weaker ones away from the food so that they can have it all to themselves.

might seem a bit mean but it's natural instinct

 

[ox5477]

And its the way natural selection helps stop sickness and disease from being spread.... the sick are exiled and kept from the healthy. Also, the genetically diseased or malformed usually will not mate so their genes will not get passed on.... nature is amazing

Ox

 

[alysonpeaches]

And its the way natural selection helps stop sickness and disease from being spread.... the sick are exiled and kept from the healthy. Also, the genetically diseased or malformed usually will not mate so their genes will not get passed on.... nature is amazing

Ox

Up to last weekend the nitrites were higher and ammonia was present and I kept doing 25% water changes, but the guy in the LFS suggested I just wait it out as my tank was obviously still cycling so I stopped. The ammonia went to 0 and the nitrites dropped, so I didnt do any more changes this week.

Should I restart water changes? I could do one today and see if it makes any difference. I am waiting until I can get new fish before I move the tank furniture as it just recently had a bit of a move when I put the java moss on the bogwood. I am planning getting some albino bristlenose catfish, but need to wait until my nitrites go to zero. I will test nitrates again, but the strips with my nitrate tests on arent very accurate. I prefer the liquid reagents as they are more accurate but I only have nitrites and ammonia tests in this form.

 

[ox5477]

well in the long run, it will slow down the cycle, but for the health of the fish, it would be best to do the water changes to minimize amount of nitrite in the water. Though, I believe zebra danios are one of the prefered fish to use in a fish cycle due to them being so hardy so maybe they will be ok. In either case, I would do the water changes again untill you see 0 for both ammonium and nitrite

Ox

 

[Miss Wiggle]

yes, start the water changes again, the fast that ammonia dropped when you stopped doing them is just a coincidence, they would have stopped anyway and reducing the nitrite will make the fish more comfortable. the link in my sig 'whats cycling' explains some more about the whole process of cycling with fish for you.

 

[alysonpeaches]

I have had a move around as Miss Wiggle suggested, but retained the large bogwood with the moss. Just moved the smaller pieces and some plants. Then I did the water change. For a while it did stop the territorial behaviour, but it has started again, just not quite so severe.

I think this male may be defending a good spawning area (over the moss). What do you think?

 

[alysonpeaches]

I am very pleased to say that today my nitrites are 0 and my ammonia is still 0. I feel like celebrating!!

The danios are behaving themselves now ... so might be ready for more fish. Just going to check that the nitrites and ammonia remain stable.

I am actually scared to do any filter maintenance in case I upset a good thing. I think I will leave it a week before rinsing it.

 

[waterdrop]

Yes, I think that's a good idea, just leaving the filter be for a week. You've just gotten it down to zeros, so you want to keep up the testing and see if the filter can hold this by itself without you doing water changes -- but do them if anything starts showing above a trace.

~~waterdrop~~