Think I figured out why my ID shark....

Chases the other one that is almost the same size.
I could be wrong, but I think it has to do with the older shark being male & the younger being female.
Right now, they are both almost the same size to where it's hard to determine who is who. Other than Sharky has a bump on his nose I call the "horn".
The younger one's lower big fin is a bit longer as in it points farther down than Sharky's does.
That lower fin seems to be the only difference at the moment.

I'll add a pic as soon as I can get one.

It could be courtship, but it could be rank. In the wild, this species shoals, and in similar species, shoals have a serious rank order. The alpha hits the number 2 who hits the number 3 all the way down the line, to establish rank. Every fish knows and fights for its place, and places constantly change. We see it really clearly with a lot of the barbs.

You have numbers 1 and 2, so number 2 will always take a bit of a beating as there is no distraction, no young lion trying to move up, and no break. In the wild, racing fish are busy with long distance swimming through serious current, and the search for food. In tanks, fish with this behavior can overdo things as they have nothing else to do but scrap. A behavior you might see a couple of times a day in the wild can happen a couple of times an hour in a tank.

There is a 3rd ID shark. He's the runt due to getting very sick when I tried to re-home him to the other large tank I have. He never gets picked on from what I can see.

He may not count in the game, whether it's hierarchy or courtship.

How big are they

The 2 bigger ones are around 14/15 inches long whereas the smaller one is is around 10 inches.
He was bought the same time as the second bigger one. But he got pretty sick to where he turned a bloaty, kinda pukey green when I moved him to the other tank.
Put him back into the original tank & he slowly went back to black. He's gotten a big bigger since.

The two fish around the same size are either feeling feisty cause it's Spring, or scrapping because they threaten each other. They aren't likely to successfully breed in your tank (they are egg scatterers) if what you are seeing is sexual behavior.

It's too bad they aren't bred in the home aquarium, as they are one of the very few freshwater species for which the aquarium trade may bear blame for their endangered status. They are being bred on fish farms now, and I doubt we're seeing many wild-caughts anymore (no one is - their population has been dropping like a brick). So they can be bred, but I expect the farms are using hormones or hormone injections, and ponds.

Yep a really big pond .and don't spawn until full grown they are getting to the size that they would normally be alone

GaryE, they've been doing it during the winter as well. I wouldn't call the actions aggressive really. Just kinda playfully chases the other one.

fish lady wrote:Yep a really big pond  .and don't spawn until full grown they are getting to the size that they would normally be alone

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