What to do with "toxic" (aggressive) fish?

[serarand]

I have a Tiger Barb that has made the environment in my tank "toxic". Right now I have it in an isolation/nursery box where he can not attack his fellow Tiger Barbs. He happens to be the largest. While in the box, the other 3 Tiger Barbs get along perfectly well and do not attack each other. When I let the aggressive one out it very soon it attacks the others so much son that they have to hide behind the heater. I used to have two more Tiger Barbs but they recently died (maybe due to injuries, who knows). I'm aware that you are supposed to have 6 or more of this type of fish. Any advice what to do?

here?

 

[Byron]

This is very common with this species, so common it is basically the norm. And it occurs when the number of Tiger Barbs in the tank is below 10. A scientific study on the effects pf too few of a shoaling/schooling species used this species as one of their test fish, and they found that in groups of three and five the fish literally tore into one another within 24 hours. The group of ten did not.

I don't know the tank size here, but there is not the slightest doubt that only having three or four is the cause of this aggression. Aggression among the species is inherent in this species, but larger groups can usually keep it within reason. It may even so go after other fish, particularly those with long fins or which are sedate. Tank mates must be very, very carefully choosen.

I don't know the tank size, so don't want to suggest acquiring 10-12 more Tiger Barbs, but that is what is needed to maintain the fish. It also depends upon other species, this may make things much worse. If you have the space, and depending upon tankmates, acquiring a group of 10-12 Tiger Barbs and adding them to the three/four you have can sometimes solve the issue.

I must also say that the detriment due to increased aggression caused by the small number of the fish is usually permanent. There is no way to tell this. Think of it as subjecting an animal to extremely stressful environment, and it causes neurological problems that are not often curable. One does not know.

 

[serarand]

This is very common with this species, so common it is basically the norm. And it occurs when the number of Tiger Barbs in the tank is below 10. A scientific study on the effects pf too few of a shoaling/schooling species used this species as one of their test fish, and they found that in groups of three and five the fish literally tore into one another within 24 hours. The group of ten did not.

I don't know the tank size here, but there is not the slightest doubt that only having three or four is the cause of this aggression. Aggression among the species is inherent in this species, but larger groups can usually keep it within reason. It may even so go after other fish, particularly those with long fins or which are sedate. Tank mates must be very, very carefully choosen.

I don't know the tank size, so don't want to suggest acquiring 10-12 more Tiger Barbs, but that is what is needed to maintain the fish. It also depends upon other species, this may make things much worse. If you have the space, and depending upon tankmates, acquiring a group of 10-12 Tiger Barbs and adding them to the three/four you have can sometimes solve the issue.

I must also say that the detriment due to increased aggression caused by the small number of the fish is usually permanent. There is no way to tell this. Think of it as subjecting an animal to extremely stressful environment, and it causes neurological problems that are not often curable. One does not know.

Thanks Byron. Very well documented! My tank is 20 gallons / 75.7 lt.

 

[Byron]

Thanks Byron. Very well documented! My tank is 20 gallons / 75.7 lt.

That is too small a space for a group of Tiger Barbs. A group of 12-15 in a 30 gallon tank is the minimum. Can you return them, or just give them to the store, or another aquarist?

 

[BeckyCats]

First, I agree with Byron, the best solution is to return or rehome those fish. That tank is way too small for that species and too sparsely decorated.

That environment is so barren. They have nothing to look at except each other and nothing to explore. Aggression is inevitable under such circumstances because there's nothing else to do and nowhere to hide. They need to be able to get out of each other's view to make the bully forget about them. He needs to be distracted by something else to do but there isn't anything to do in that tank.

To keep this species, you'll need to get a larger tank, put plants and other things in it to make a nice habitat, and then get more of the barbs. It's the same with many species. They prefer larger numbers of their own kind and a more natural environment for them to feel like they can hide and to forage for food, etc.

Regards of the type of fish you get, there really needs to be a proper environment for them to live in. Fish are live animals to care for, not decorations to be viewed. Some plants that grow tall and other decor is needed in there. I see a couple of little plants at the bottom. Are those real? You will want to put in something else tall in the meantime while that grows.

I will say that it can be difficult to provide a good home for many species in a tank with that shape being so much taller than it is long. There isn't a lot of room to swim from side to side and the fish are almost always on "top" of each other which can be uncomfortable for a lot of fish types. Try posting a new thread to ask what kinds of fish people recommend in that type of tank.

I posted some pictures below of 20 gallon octagon tanks that have good proportions of decorations that would be more likely to make fish feel more comfortable.

Best of luck to you and your fish!

 

[Essjay]

The problem with tall narrow tanks is the lack of swimming length. The volume should be ignored and the tank stocked with fish suitable for the side to side measurement. A tradional rectangular tank is much easier to stock and volume for volume they have more swimming length, so fish are not restricted to very small slow swimming species.

 

[BeckyCats]

Hi,
I've been thinking about your little barbs. How are they doing? Have you come to a decision about what you want to do (re-home/ return them or get a bigger tank for them)?

The tall octagon tanks are very pretty and I was tempted to get one myself when I first started fish keeping. Folks on this forum steered me away however because of the issues raised above (can't keep much in them and it's unsuitable for many species), plus the visibility problems of the many sides creating visual jogs. However, now that you have it, there are certainly fish that would be happy in it. Mostly small little fish that will be happy to swim up and down rather than side to side. Of course you also have find something that will be happy in your water type (hard vs soft, etc.) but if you are able to get that info together and post a new stocking-suggestion request thread, I think you'll be able to find something.

 

[serarand]

Hi @BeckyCats, thanks for your very informative postings. The plants that you see are plastic, there is also a moss ball but I did not have that much luck with that one and it seems to be dying. Lately my plants have to not been doing good. I used to have some plants in the tanks (amazon swords) but they have been dying or maybe the 2 mystery snails that I have eat the plants or something but long story short... the plants have not been lasting. I agree with you, the tank is barren and improvements need to be made. I think I probably need to return these fish and get some guppies that are more suitable for this tank. The Tiger Barbs were OK when they were 6, but 2 died and now we ended up with a very aggressive fish.

 

[FishLady18]

I keep 11 together. No problems yet. No other species with them

 

[plebian]

That is too small a space for a group of Tiger Barbs. A group of 12-15 in a 30 gallon tank is the minimum. Can you return them, or just give them to the store, or another aquarist?

I agree with most of what you've said, but disagree about the tank size. Barbs are very active and require a lot of swimming room. A 3 foot tank won't provide enough. Although it's absolutely possible to keep a large number of fish in relatively cramped quarters, given adequate filtration and water changes, as you noted you will not see normal behavior under those circumstances. I would suggest a 40 gallon long as the absolute minimum for a group of barbs. You could of course keep one or more compatible bottom feeders in a tank that size as well.

 

[BrianK]

I had a group of 12 tiger barbs (down to 7 now). I had one the was very mean. He chased all the others so they were hiding all the time while he cruised the tank all by himself. After 3 literally stopped eating and died, I removed and killed the bully. The remainder have been peaceful ever since. I am still replacing with serpae tetras as they die (lost a couple to fin rot also when put in some fish that I didn't know were sick and didn't quarantine).

 

[GaryE]

The problem is you have a 20 gallon 5 gallon tank. Volume doesn't matter nearly as much as base dimensions. If you have a three foot front glass tank that was only 4 inches tall, those barbs would love it. But the cylinder shape is really a one fish tank. The fish have nowhere to go, and aggression is amplified. No fish has ever been a bully. Many fish have been kept in impossible for them tanks - it always comes back to the space we give them.

 

[plebian]

The problem is you have a 20 gallon 5 gallon tank. Volume doesn't matter nearly as much as base dimensions. If you have a three foot front glass tank that was only 4 inches tall, those barbs would love it. But the cylinder shape is really a one fish tank. The fish have nowhere to go, and aggression is amplified. No fish has ever been a bully. Many fish have been kept in impossible for them tanks - it always comes back to the space we give them.

Seriously? Did you not understand "I removed and killed the bully. The remainder have been peaceful ever since." You may not like the term bully, but it describes the observed behavior perfectly.

From Miriam Webster, bully: "one who is habitually...threatening to others who are weaker, smaller, or in some way vulnerable."

I've also had to deal with bully fish, and simply removing the bully solves the problem. I've already stated I think the OP should have a larger tank, but having a larger tank will not change the behavior of excessively aggressive fish.

Just for reference, I housed 5 Discus in a 180 gallon (9ft long) community aquarium and one Discus terrorized all four of the others to the point they stopped eating. Removing the bully solved the problem. Tank size had nothing to do with the observed behavior.