Sudden Bloodfin Tetra Aggression

[Merilial]

HI all,

I've had a school of 7 bloodfin tetra for nearly 2 months now with no incidents. However, in the last week, I lost two of the tetra -- both had chunks taken out of their fins, but I chalked it up to the carcasses getting picked on.

However, the last few days my neon tetras also have nipped fins, as does my single male guppy who used to boss the bloodfins around. The straw that broke the camel's back was when I saw the bloodfins attacking one of my albino cory cats, who is now missing about half tail fin.

Tomorrow I'm going to call my LFS and see if they'll take the bloodfins so my question is this: why the sudden aggressive streak? I divided my tank for tonight, and the bloodfins are now nipping and tearing up each others fins. It seems like they're just attacking whatever is closest at the time.

I do not plan to get more tetra (the bloodfin were a gift, and I lost half my original neon school to Neon Tetra Disease). I'm just curious what the thoughts are on this, and if anyone has had something similar happen.

 

[Goodbye]

Do you still have the fish listed in your profile in addition to the 7 bloodfins in a 20 gallon tank?
If so, your tank may be overstocked. Crowded conditions inevitably will cause aggression.

 

[Merilial]

Do you still have the fish listed in your profile in addition to the 7 bloodfins in a 20 gallon tank?
If so, your tank may be overstocked. Crowded conditions inevitably will cause aggression.

I'm in mobile, but I'm fairly certain it's out of date. I lost most of my neon tetra school, and only had 3 remaining, the single guppy, and the cories. I knew the stocking was pushing it (my parents got the fish for me while I was at school because they knew I was sad about losing 7 of my neon tetras) and I was hoping to give my remaining neons to a friend.

Stocking seems the most plausible to me, I'd agree with that.