Black skirt tetras killing each other

Hi there, I'm new here and couldn't find anything related to this particular topic and was looking for advice.
I have a 120L (approx 40 gallon?) Well established tank that I've had running for about 4 months. I originally started it as an upgrade for my two black skirt tetras, I stocked it with 4 more making 6 black skirts (2 young males and 4 adult females) and then adopted an angelfish who sticks to himself and causes no problems. The angel and tetras avoid each other. But over the last couple weeks I've had two fish get injured, one female had her gill plate ripped out and passed away and now 2 weeks later another female has had half her top lip bitten off. I've never had any issues other than these, i was wondering if anyone can help me out and knows about black skirt tetras being aggressive towards each other and how you fixed it?

I know it's not the males being aggressive as I've observed them and am pretty sure it's the females being aggressive.
Thank you for any help I can get and I apologise for the long post but couldn't find any information elsewhere!

 

No offense, but why would you keep angelfish with long, delicate fins with black skirt fin nippers. If the angelfish is large, it can attack the black skirt tetras.

That happened to my young male. It died within 5 minutes because of nipping i think

 

No offense, but why would you keep angelfish with long, delicate fins with black skirt fin nippers. If the angelfish is large, it can attack the black skirt tetras.

The angel fish was in a situation where another angel fish was attacking him and my tetras have never hurt him and he's never hurt the tetras. His fins are starting to grow back from being bitten off by another angel fish (wasn't mine) and they've never hurt him nor does he hurt them, they each have their own space in the tank and feeding time never shows any issues either, when he gets bigger my plan is to remove him and put him in a more suitable community tank, but I've never had any issues and I've heard of people successfully keeping angels with black skirts for years.
More worried about the black skirts attacking each other, I figured if it was the angel fish who'd done either of the injuries to the black skirts he would have ultimately done a lot more damage.

I do however understand your concern but I've never had issues with them hurting him, I think I've gotten the luck of the draw with non fin nipping tetras and a non aggressive angel fish, they just seem to be hurting each other.

 

Hi Fishgirl1234,
I have seen tetra aggression. Adding new fish to an established group will mean they have to sort out who is who in the order of dominance.
I have seen the worst behaviour from tetras when the water had unsuitable parameters.
All I can suggest is a few extra water changes. Temperature matched conditioned water.
Move some ornaments around as you would in a cichlid tank, it can do no harm.

I also think 6 tetras is not enough to spread aggression. I know what the internet says about numbers. I currently have quite a few species of tetras in large groups. I had 15 black skirt tetras not long ago.

 

I think it is the Angel nevertheless and I think "agression in the Black Skirts is natural behaviour.

 

You probably should get the angel in a different tankthey are not compatible with black skirts

 

You probably should get the angel in a different tankthey are not compatible with black skirts

I think if the angel had done the damage they would've been more serious and probably larger injuries to be honest, and the tetra don't honestly bother him and at the moment I have no other place to accommodate him. I have observed them for a long time over the last few weeks and the angel shows no signs of aggression towards the tetras and mainly just relaxes in the tank. After watching the fish yesterday at both feeding times and then coming home to see my whole school of tetra except one huddled on one side of the tank, I have realised that it's just one sour female tetra that keeps chasing and nipping very aggressively at the others. My LFS has offered to take her back and exchange her for another one because she isn't socialising well. I also had another fish owner tell me it's quite common to have one bad fish amongst schooling fish and that it's happened to him a few times too.
Thank you for all your advice though, and when the angel fish does start becoming a problem (he is only about half grown and shows no signs of aggression) I will of course have to find a more suitable place for him but keep in my mind I always have used caution and kept a close eye on him while having him in my tank I always feed them on separate sides of the tank otherwise the tetra seem to startle him and steal all his food. I even added him after the school of tetra had a few weeks to settle (the first fish death was before I put the angel in as well) so i will wait until he gets larger, but once again I do know that angels and Black skirts are something that you shouldn't keep together but have also heard experienced fish keepers saying they will do fine as long as you use caution, have your water parameters stable for both fish's needs and have a backup tank in case anything goes wrong and I went into it knowing that if my fish began chasing the angel I would remove him for his own safety. But the angel had previously come from a large community tank anyways so nothing really bothers him.