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naitch1980

Aquarium Advice Apprentice
Joined
Sep 19, 2006
Messages
17
My tank has been settled for some few months now and suddenly, out of the blue, my Penguin tetras have started to attack one another and other fish.

I've had the 5, as a settled group, for about 3 months now, and two have suddenly begun attacking the others, killing one and now picking on another one.

One seems to "defend" the left side of the tank, the other seems to "defend" the right.

Any ideas what this could be? I thought Penguins were quite placid fish.
 
I can't remember the volume of the tank, but it's about 30 inches by 15 inches by 20 inches.
Tank mates are same as they were from the beginning 6 neons, an angel fish and 2 clown loaches. No new food, no new ornaments, only thing new could be the 20% water change I did last week
Water conditions are all normal.
 
Could be aggression if they are getting larger (same tank space with fish getting bigger = less tank space), but more than likely they are feeling the need to mate. Any new colorations or displays other than aggression?
 
To be honest, no, everything is exactly the same. They're slightly bigger maybe, but nothing to write home about.
Either way, they've killed one of their own and looked likely to kill another yesterday. With it being a sunday though, it's not like i could've popped out to buy a birthing tank or anything like that to seperate them temporarily.
 
Sometimes aggression just comes about for no good reason (to us at least). They can suddenly become less stressed in the tank and now those previous fish they schooled with are now competition. You can always try to break up the line of sight in a tank with ornaments/plants/driftwood, but its not a guaranteed fix. I would get a breeder cage just in case one of your fish gets heavily damaged. They can then recoop in there for a while. Ideally you would want a QT tank.

When I first started one of my corys and one of my barbs were picked on at different times. They both spent a week or 2 in a small breeder box floating at the top of the tank. Not fun I'm sure, but it was better than getting nipped to death or possible infection. I've since purchased a 10gallon QT tank that sits under my main tank and am currently breeding snails in it. If any of the fish get injured in the main tank, I'll transfer them over. I have the same water conditions in both so the switch is just done with a net, no acclimation needed (I do 50% PWC from the main tank into the lower tank prior to fish transfer just to be sure).
 
Hi there,

Naitch's other half here, I noticed you asked about a colour change, I had ntoiced that it is very very very slight but there is a slight shade of pink in the tetra, not the attacked fish, but the attackers!
I dont no if this would be of any help to understand what is happening.

Cheers
 
Possibly male coloration to "attract" the females for mating. My barb whom needed to be removed from my tank due to uncontrollable nipping at the female in attempts to mate turned bright red on the underbelly and fins (he's a hybrid cherry gold barb so its much more pronounced than other fish).

Sounds like they are competing for a mate. Normal avenues to reduce this aggression is to increase the number of females if only a couple (they might be the ones getting killed), or increasing the number of males so they can establish a pecking order amongst themselves.

With my barb, I had a fully stocked tank and so he had to go. He spent a couple weeks in a 10gallon QT tank, and now lives by himself in a 5gallon tank at my SIL's office.
 
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