Fish suddenly showing aggression

mrsjoannh13

Fishaholic
Joined
Nov 2, 2020
Messages
574
Reaction score
439
Location
USA
I have 2 new long fin white skirt tetras in a quarantine tank. They have been in it for about a week and came from the same tank at the pet store. They have always co-existed fine. This morning I had a bit of an ammonia spike in the tank so I had to do almost a complete water change. Since then, one of the two has been "going at" the other one. Wherever the one fish goes the other one seems to chase after it and try to have a go at it. One fish is just kind of dive bombing the other one. There is no fin nipping... just the dive bombing for lack of a better explanation. And it's pretty relentless. I'm very worried that the fish is going to get stressed from the aggressive behavior of the other fish but I didn't really want to move them into my display tank just yet as they have not been in QT long enough. Any suggestions? Is this normal for them to be aggressive maybe due to stress from the big water change? Any help appreciated. Thanks!
 
These are shoaling fish which need to be in a group of at least 6 with more being better. When kept in too small a number they get stressed and stressed fish either become reclusive and hide or they become aggressive. It is also likely that they have started sparring to decide which one is the alpha fish.

Will they be going into a tank with more white skirts or will they be the only ones?
 
These are shoaling fish which need to be in a group of at least 6 with more being better. When kept in too small a number they get stressed and stressed fish either become reclusive and hide or they become aggressive. It is also likely that they have started sparring to decide which one is the alpha fish.
Yep, it's clear one of them has established themselves as the alpha! I do have several of these tetras in my large tank and planning to add the to that after they QT.... if they survive! I am hoping they settle down shortly. Any suggestions on what to do if the one keeps going after the other until I can add them in the larger tank with the others?
 
Yep, it's clear one of them has established themselves as the alpha! I do have several of these tetras in my large tank and planning to add the to that after they QT.... if they survive! I am hoping they settle down shortly. Any suggestions on what to do if the one keeps going after the other until I can add them in the larger tank with the others?

Ok what size is your tank ( length width and height ) and how many of these white skirt tetras are in there already?
 
The main tank (established one) is 10 gallons (20 x 12 x 12) but I am going to upgrade to 20 gallons (24 x 12 x 16). There are 4 of them in there right now. They have been in the tank for a month or so and all doing fine. No aggression from any of them.

The QT tank is small - about 5 gallons - it's a small bow-front. I have some artificial plants in there to give the 2 new fish some hiding spots. They have been fine with each other the past week until I did the 75% water change this morning. I'm really concerned for the fish that is getting dive bombed.

Appreciate any suggestions.
 
That's the other problem - the tank size. If they were my fish I would move them in with the others despite quarantine - and upgrade asap as they do need a tank bigger than 10 gallons as they are quite big fish.
 
Ok, I'm not an expert regarding fish but keep an eye on the fish that is getting dive bombed. When are you going to move the fish out of the quarantine tank? Is this in inches, the 20 gallon, or centimetres.

Are the fish suited to your water parameters?
 
As @essjay said above, they would probably get a bit big for the 10 gallon so probably moving thoe fish to the 20 gallon asap is probably the best idea as the one that is dive bombing may drop his attitude when he gets out of the QT.
 
That's the other problem - the tank size. If they were my fish I would move them in with the others despite quarantine - and upgrade asap as they do need a tank bigger than 10 gallons as they are quite big fish.
Yep, that's where my head is. I do still need to silicone seal the 20 gallon and leak test it. So that's a 2-3 day process before I get it set up. But I might try to move them sooner rather than later. The 2 new ones are a bit larger than the others so I'm hoping the aggression doesn't carry over into the new tank when there are 6 of them.

would you move the 2 new ones right now into the 10 gallon? Or wait until I can get the 20 gallon set up.
 
As @essjay said above, they would probably get a bit big for the 10 gallon so probably moving thoe fish to the 20 gallon asap is probably the best idea as the one that is dive bombing may drop his attitude when he gets out of the QT.
If I didn't have pesky work tasks I would jump on the tank upgrade right now. My schedule probably won't allow it until this weekend but I feel like I have to do something. I can't stand to see the one getting stressed out and so angry for myself for not doing a better job of planning.
 
If I didn't have pesky work tasks I would jump on the tank upgrade right now. My schedule probably won't allow it until this weekend but I feel like I have to do something. I can't stand to see the one getting stressed out and so angry for myself for not doing a better job of planning.
I feel for you on that one. THe fish have been quarantining for a week you said? And they are not showing any illness? It might be ok for you to move them to the 10 gallon. @essjay will help out as well as she is way more experienced than me:)
 
I feel for you on that one. THe fish have been quarantining for a week you said? And they are not showing any illness? It might be ok for you to move them to the 10 gallon. @essjay will help out as well as she is way more experienced than me:)
Yes it's been almost a week. They look great. Healthy, previously calm and content, eating well. Clear eyes, fins and scales. No poop issues, etc.
 
Yes it's been almost a week. They look great. Healthy, previously calm and content, eating well. Clear eyes, fins and scales. No poop issues, etc.
To me they sound fine but as I said I'm not experienced so I'm not really sure. I think they can be moved however
 
Another option is a tank divider for the 5gal. Again, not an ideal solution but where you are QT'ing them they should make it through. If I went with that route I would keep the lights off completely and make sure there are live plants (floating ones are fine) to help ease the stress.

Did you prophylactically treat w anything during QT? If you did a salt or deworming treatment it might give you more "mental security" to transfer them into the main tank sooner.

I think this is a tough balancing act since you want to ensure all the fish's health (including ones in the main tank), but stress can also be a negative impact on health.

Good luck, I think any decision you make at this point is a justifiable one.
 
Another option is a tank divider for the 5gal. Again, not an ideal solution but where you are QT'ing them they should make it through. If I went with that route I would keep the lights off completely and make sure there are live plants (floating ones are fine) to help ease the stress.

Did you prophylactically treat w anything during QT? If you did a salt or deworming treatment it might give you more "mental security" to transfer them into the main tank sooner.

I think this is a tough balancing act since you want to ensure all the fish's health (including ones in the main tank), but stress can also be a negative impact on health.

Good luck, I think any decision you make at this point is a justifiable one.
I did put aquarium salt in and the recommend dose on the carton and replaced it when I did the previous water change. Nothing more than that as I haven't seen any other signs of distress or disease. Other than the aggression today they have been doing great.

This is my daughter's tank (the 10 soon to be 20 gallon one) and I would hate for there to be any issues with her existing fish due to the addition of these 2 new ones. The new ones are bigger than a few in the established tank so if there is any bullying in there I may have to return them to the pet store (they said that was an option).

I did have the lights on and blinds open when I did the water change. That may have added to the stress. I closed the blinds and turned off the room lights a little while ago. I *think* they are settling down a bit. I am going to keep an eye on it.

In the meantime, I appreciate all suggestions and input. I am pretty new to the hobby and try to do a lot of research before making decisions but clearly still make mistakes.
 

Most reactions

trending

Staff online

Back
Top