Agressive, fin nipping Diamond Tetra - help!

[StellaStars]

I got four Diamond Tetras a week and a half ago for a new 23G tank.

It's moderately planted and decorated with some hiding spaces.

One of the four was a huge bully, doing some serious fin nipping damage.

Today, I got four more (the water params had settled down) and the lfs clerk got all females for me, saying that the bully was likely a male and that this would help.

I had hoped that the larger school would fix the problem.

Well, it's only been a few hours but he's bullying all of them now.

He gets one side of the tank to himself while the others hide on the opposite side.

I specifically wanted a peaceful tank and this is the opposite.

Do I need to give them more time to settle down or do I need to get him out of there?

I did try to net him and failed utterly. He's very fast moving.

Help and advice would be very appreciated.

 

[Fresh2o]

Would have been nice if the added stock calmed things down. I had the same thing happen with 7 zebra danios. Dominant female occupied one half of a 20 long and attacked and chased any fish that approached. Tank was heavily planted and the aggression subsided eventually (quite a while later...maybe weeks/months!)
Try a two net technique; use a smaller 3-5" net to chase the intended fish into an 8-10" or larger net.


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[mrvincent]

Add hiding spots

 

[StellaStars]

There are a decent number of hiding spots.

Right now the bulky seems to have claimed one third to one half of the tank and is chasing any fish that crosses that line.

I'll go pick up a bigger net and see if that makes him easier to catch.

If it doesn't, and I just have to wait and see if he settles down, I'm wonderful what this will do to my stocking plan.

Do you think the bullying would be restricted to the other diamond tetras or would he bulky any fish in the tank?

 

[ScotJudd]

I think if you want to keep the bully you either have to net him or add more fish. I had minor bullying by a variety of fish but now that I'm fully stocked there's no bullying. A single fish can only keep so many other fish at bay.
Just a tip for netting him. Put a large net in the tank (not a white net) with the netting pulled out and leave it there for a few minutes. Then guide the fish into the net using a smaller net keeping the small net moving. He won't even see the big net if it's not moving. I actually guide the fish into the big net with a bamboo cane which takes patience but doesn't unduly upset the rest of the tank. Strangely enough the fish aren't as spooked by a cane as they are by a net and I find it easier to calmly guide the fish into the catch net.


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[gemach7]

I think if you want to keep the bully you either have to net him or add more fish. I had minor bullying by a variety of fish but now that I'm fully stocked there's no bullying. A single fish can only keep so many other fish at bay.
Just a tip for netting him. Put a large net in the tank (not a white net) with the netting pulled out and leave it there for a few minutes. Then guide the fish into the net using a smaller net keeping the small net moving. He won't even see the big net if it's not moving. I actually guide the fish into the big net with a bamboo cane which takes patience but doesn't unduly upset the rest of the tank. Strangely enough the fish aren't as spooked by a cane as they are by a net and I find it easier to calmly guide the fish into the catch net.


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If you can get him out of there into a quarantine tank for a bit. Sometimes giving an aggressive fish a cool down period while the rest of the school reforms a hierarchy without him can get him to be more peaceful if added back to the tank after a week or 2. I do notice with my diamond tetras the runt male is sometimes chased by the largest male out of the school to a side of the tank. the runt is still healthy and eats everyday and this has been going on for about a year without any fin damage to any fish.


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[StellaStars]

Finally got the bully out. I had to dismantle the tank and drop the water to about 6 inches to do it. Very frustrating. Some of the plants seem a little worse for wear.

It's interesting to see how the behavior of the other fish has changed now that there isn't a bully/predator in the tank. They don't swim together nearly as much.

This experience has made me a lot less willing to experiment with stocking that might include personality conflicts - I never want to have to get a fish out of the tank again!

 

[Rivers2k]

I had the same issue with Columbian red fin tetras. I thought well this is no fun I wanted a nice schooling fish. I got rid of all the tetras and now have a baby swimming in the tank. I guess it was them breeding. Maybe yours was the same.