It looks like having only 4 may be a problem. It can also be worse if the tank is crowded. Take a look at the behavior info on these links:

http://www.seriouslyfish.com/species/knodus-borki/
http://www.aquariumlife.net/profiles/characins/blue-tetra/100133.asp

 

It looks like having only 4 may be a problem. It can also be worse if the tank is crowded. Take a look at the behavior info on these links:

http://www.seriouslyfish.com/species/knodus-borki/
http://www.aquariumlife.net/profiles/characins/blue-tetra/100133.asp

great info.
thanks a bunch,
big o

 

I also have seen more aggression from Blue Tetras than from most other Tetras. I would rank them as less of a problem than Serpaes, or Tiger Barbs, but they are not totally peaceful fish.

 

I just ordered 12 of them, only 9 survived shipping to my lfs - they are in a 10g QT tank now. I bought them because everything I read said they were a schooling/shoaling fish, but that's not happening in the QT tank. I realize there isn't any reason for them to shoal while they are by themselves. They will eventually go in the 125 with the Columbian and Buenos Aires tetras - the Buenos can be very assertive - I thought that would encourage shoaling from the Blues - maybe not! lol I am seeing so much aggression in the 10G that I wonder what the Blue tetras will be like in the community tank. I'm hoping 9 will be enough for them to stick together and keep the squabbles within the family, so to speak. But if they just chase each other around nipping, and disrupt the tank, that will get on my nerves fast.

 

I had a school of 5 in my community tank and they did fine in my opinion. They did a little chasing here and there but only amongst themselves and it was nothing aggressive. They were housed with guppies, endlers, and ottos and they were not aggressive to any of them.

I will say though that they mysteriously started dying off one by one and only have 2 left, and they show a lot of aggression now that they cannot school.

6 or more IMO would work or if they were with similar sized tetras I would think.

 

If these 9 do well in the tank (it will be a while before they come out of QT) I'll add to their school. I just saw today some video by a member - can't remember who off the bat - that has 50 of them in a 180g tank. They looked wonderful swirling about! It wasn't schooling as I think of it, more like a loose rolling ball with break-away parts - still very lively : )

 

LOL, good luck with the blue tetra! I had one that managed to get mixed in when I bought other fish from the big box store. Terrorized my 48 gal tank by itself. I tried to give it away to club members but I don't really remember what happened to it. Hmmm. Now I think I'm getting old.

 

I've got about 50 blue tetras in my 165 with Roseline Barbs. They are very aggressive. Go for a large school so they pick on themselves... they chase each other around a lot. They eat more viciously than the Roselines as well:

http://www.youtube.com/watch?v=3edz0oKRU0U&feature=youtu.be

 

Ah! Yours is the tank I was talking about - don't know why I had 180g in my head. Your vids are fantastic!

Maybe I'll wait and put the Blue tetras in a 55 I'll be setting up in a few months...the 125 I bought them for has Columbian tetras, Buenos Aires tetras, plus a few leftovers from a tank I took down; 5 black neons and 4 Harlequin rasboras. I wonder if they can possibly be more aggressive than the Buenos Aires? A 55g tank full of Blue tetras could behave like a mini version of your tank - I love the activity.