Penguin Tetra Aggressive

[han19]

Hi,

My brother had a tank with other tropical fish and four penguin tetra unfortunately three of the penguin tetra died a couple of months ago but recently we noticed that the remaining penguin tetra was aggressive towards the other ones even killing three if the small tetra living in the tank. So we moved the penguin tetra to another tank and talked to some shop owners of aquariums that said we needed to get more penguin tetra to live with it as they live in big groups in the wild. So we now have the old penguin tetra and three new ones, there are also two young angel fish in the tank with them.

Now the problem is that the original penguin tetra is attacking the other penguin tetra, he seems to be herding them up into one corner and then trying to bite them. He doesn't bother about the Angel fish. I have noticed that he is more aggressive when it comes to feeding time.

If anyone has any suggestions that would be great.

 

[Fishfriend1]

Increase the school size from 4 total (1 oldie and 3 newbies) to 8 (1 oldie and 7 newbies). That *should* spread out the big one's aggression over all of the smaller ones and reduce stress on any 1 fish.

 

[Byron Amazonas]

This might help (increasing the group to 8+). But it might not.

Fish that are shoaling (some call it schooling) by nature, meaning that they live in groups of hundreds together, must have several of their own species in the aquarium. Most sources will suggest six as minimum, but more is always better, and in some species essential. This applies when you first acquire them. As the fish mature, they develop interactions within the group. When there are too few of the species, it can affect the fish in a couple ways. The more common is increasing the natural aggression. Aggressive fish by nature become even more aggressive, and otherwise peaceful fish (like these penguin tetra) can turn aggressive. This is now a proven scientific fact. The unfortunate side to this is that the damage caused to the individual fish from this severe stress is often permanent. In other words, increasing the group after the fact may or may not correct the problem. There is nothing you can do to "fix" the internal fish problem. If with the larger group the same fish still is aggressive, it is best to remove it and euthanize it. The stress this "bullying" causes to the other fish will cause similar reactions in them over time, or it may be the opposite...they will become too timid to even eat. Either way, it is damaging to the entire community.

I hope this helps to explain the issue.

Byron.

 

[RobShort]

Just joined the forum today to look into this very thing. Luckily, it seems I stumbled into the correct solution by chance. I had a community 10-gallon tank with two surviving Penguin Tetras who had become very aggressive toward each other and the rest of the fish. I had already lost 4 Penguin Tetras, 2 Scissortail Raspboras, and 2 "Brilliant Tetras" (or so the store called them) because of the Penguin Tetras' aggressiveness. I removed the 2 Penguins and added a few more community fish (Black Neon Tetras, Plattys, a Dwarf Gourami) and all have been getting along very well for the past month now that the Penguins are gone. The remaining Brilliant Tetras seem to shoal very agreeably with the Black Neon Tetras and the Dwarf Gourami keeps happily to himself. Unfortunately I didn't yet know that it's better to have several of the same shoaling species together rather than small groups of different species when I added the most recent fish, but they seem happy together.

Removing the aggressive Penguins seemed to do the trick. Wish I had been able to read Byron's post 2 months ago - might have saved my previous community. But at least now I have happy fish and seem to be on the right track (especially after finding this place!).

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