What Exactly Constitutes "Too Aggressive"?

[nike12301]

A couple months ago, I bought an electric blue Jack Dempsey to go in my community tank. I know -- it was a bad idea. It was an impulse purchase when the guy at the store told me EB Jack Dempseys are usually pretty peaceful. So I've been trying it out ever since then and there have been no problems. Maybe he was right.

Here's my question...

He's still less than three inches, and I've been keeping a close eye on him obviously to see if he is too aggressive with the other fish. I have noticed on a few occasions that he'll dart after one of the other fish for just a second and then stop and go back to his business. No more than that. No biting, no fighting, nothing. Just one quick chase and that's it. But this is no different than what I've seen my rasboras do on occasion, and they're harmless. So at what point do I decide that he's too aggressive and he is a threat to the other fish? What are the signs? What will he be doing?

I don't mean to be a jerk, but please don't respond telling me what a bad idea this is. I know it's a problem situation, I'm trying to monitor the problem and see what to do next. What are signs of truly aggressive behavior in fish? Because I don't think I see it yet.

 

[drobbyb]

You are witnessing classic territorial behavior. He's just chasing the other fish out of his area. Once he gets big enough he may eat the smaller fish in the tank, but I'm sure you already know this, so that's all I'll say on that subject.

If this becomes a problem where he is harming the other fish, you can always rearrange the tank to force him to claim another territory.

 

[waterdrop]

Agree with Robby. Its my guess that the "change" will take place in the blink of an eye one day. Right now the territorial chase quickly ends as some instinct tells him his mouth size is still too small and the chase has done its job. At some point, one day, without warning, his instinct will just reach the conclusion that this fish he's chasing can easily fit in his mouth and -snap- it'll be gone and a new sense of double satisfaction (who knows, lol) will suffuse his little brain.

~~waterdrop~~
ps. plenty of sympathy for ya, I used to have Jack Dempseys and they can be beautiful!

 

[nike12301]

Agree with Robby. Its my guess that the "change" will take place in the blink of an eye one day. Right now the territorial chase quickly ends as some instinct tells him his mouth size is still too small and the chase has done its job. At some point, one day, without warning, his instinct will just reach the conclusion that this fish he's chasing can easily fit in his mouth and -snap- it'll be gone and a new sense of double satisfaction (who knows, lol) will suffuse his little brain.

~~waterdrop~~
ps. plenty of sympathy for ya, I used to have Jack Dempseys and they can be beautiful!

Ok thanks. So here's a thought... suppose I always make sure to keep the Jack Dempsey in with only fish that are too big to fit in his mouth? Wouldn't that keep things safe for everyone?

 

[drobbyb]

Safe from being eaten, yes. Fish can be killed by being stressed or harassed to death, so I wouldn't say that they are safe.

 

[waterdrop]

Yes, have to agree with Robby again, if you decide to keep at if for a while it will be important to try and understand what symptoms of stress look like (avoidance swimming, pale colors..) and take actions to end the community situation if you suspect you are seeing them.

There may be Dempsey experts who could pop up here and give us a full run-down of the possibilities but I used to always keep my dempseys either alone or as a pair and the only ones in the tank.

~~waterdrop~~