Banggai Cardinal Pair Aggression

Zakary2003 · Nov 16, 2024

I recently bought a pair of banggai cardinals. They were and still are really small and couldn't be sexed. They've been in my tank for over 10 days now. One is very active and is eating well and swimming throughout the tank. The other hangs out in the top corner or at the back of the rock structure and is far less eager to eat. I've seen the more active one pick on the one in the corner a couple of times, especially at night, but neither show any signs of damage like tattered fins and such.

Is there a chance they are still opposite sexed and just haven't paired up yet, or are they both males? Should I rehome one of them now or keep waiting it out? If I do rehome them, should I rehome the aggressor or the less active one?

I can attach pictures if requested, but there isn't any clear anatomy. I already had a friend who formerly bred banggais and pj cardinals take a look and he couldn't sex them.

Peace River · Nov 16, 2024

There are several faint indicators for sexing bangaiis including jaw line etc. They are sneaky aggressive to their peers and when I have kept them, I start with a group and invariably it has dwindle to one (which then survived for an extended period). I'm sure other have different experiences and hopefully will chime in soon, but bangaii aggression can (not always) be a concern. Good luck!

Zakary2003 · Tuesday at 3:33 PM

Nothing has changed since I made this post except the one that was lethargic is more active now and hides inside the rock structure instead of in the corner. The one that was more active is still being agressive.

Can anyone offer some suggestions?

My friend in the hobby says I should add a third cardinal and see if two of them pair up and then rehome the third wheel.

Does anyone have an opinion on that?

F i s h y · Tuesday at 3:49 PM

I breed and raise Cardinals. what you are describing is pretty typical sibling aggression. This is how the strongest one makes sure it gets more food than its siblings regardless of sex. They are not typically sexually mature or able to be sexed until close to 1 year old in my experience. Some as early as 9 months. Sexing is quite difficult for anyone that has not had extensive experience with them. Additional cardinals may in fact curb some of the aggression, and as they get older, you will likely get a pair if there are opposite sex individuals. I have only been able to keep more than one pair successfully in a 6 ft long or longer tank. in my experience anything less and a single pair will hunt the others down and kill them. My current breeding pair is nearly 4 years old and i have 3 current clutches of babies. They live in an 8 ft (360 gallon) mixed reef as the only pair.

If you have a large enough tank, my typical school size i start with is 5. this usually yields at least 1 pair. once the pair forms, then the others should be rehomed.

Zakary2003 · Tuesday at 3:51 PM

F i s h y said:
I breed and raise Cardinals. what you are describing is pretty typical sibling aggression. This is how the strongest one makes sure it gets more food than its siblings regardless of sex. They are not typically sexually mature or able to be sexed until close to 1 year old in my experience. Some as early as 9 months. Sexing is quite difficult for anyone that has not had extensive experience with them. Additional cardinals may in fact curb some of the aggression, and as they get older, you will likely get a pair if there are opposite sex individuals. I have only been able to keep more than one pair successfully in a 6 ft long or longer tank. in my experience anything less and a single pair will hunt the others down and kill them. My current breeding pair is nearly 4 years old and i have 3 current clutches of babies. They live in an 8 ft (360 gallon) mixed reef as the only pair.

If you have a large enough tank, my typical school size i start with is 5. this usually yields at least 1 pair. once the pair forms, then the others should be rehomed.

My tank is definitely not large enough for that. It's 20 gallons. They are the only fish in there at the moment, but I think 2 is pushing it as is. Luckily there are plenty of hiding spots.

F i s h y · Tuesday at 4:00 PM

Zakary2003 said:
My tank is definitely not large enough for that. It's 20 gallons. They are the only fish in there at the moment, but I think 2 is pushing it as is. Luckily there are plenty of hiding spots.

An adult pair would be pushing it in a 20 Gallon with any other fish. By themselves they would be fine.