Why are my neon tetras singeling out individuals and bullying them to death?

[bakeneko]

I hope that someone can help me with this. I recently bought a new aquarium (50 litre. 60x30x35) and put 30 small neon tetras in it. Only afterwards did I realise that I should have gone with fewer since I need to have the tank cycle first. I have been trying to get this to happen smoothly without having any fish die, but this has not gone so well. I lost a fish while doing a water change and now I lost another one today, but this was because the other neon tetras in the tank was taking bites out of it till it basically died from fear/stress/having no fins left. I separated the victim from the the rest but by the time I did it was too late. It swam a little but then expired.
my ammonia level is pretty high (1.5mg/l). Its been like this for two weeks now, and doesn't change, even after water changes.

This is what I have. I would try and figure it out by myself more, but I dont want more fish to die, so if anyone has any ideas, I would be very grateful.

I think I have included all the relevant information, but if I am missing anything, please let me know and I will try and provide it for you.

 

[prsturm]

Mother nature is a harsh mistress.

I don't have a specific answer, but a general biological phenomenon is that among organisms with schooling or herding societies, weakened or sickened members have been known to be "de-selected" by the herd. If the weaker fishes are succumbing to ammonia poisoning, the others are killing them. Depending upon how you look at it, it can be viewed as "mercy killing". It might be a natural response and a way to reduce ammonia production to boot. Of course, in a tank, the dead fish don't get washed away, so this is worse than letting them live, since the decaying body will produce a spike in ammonia.

Or, they're all just pissed off by the water condition and are taking it out and expressing anti-social behavior.

 

[lauraf]

30 neons in a 50litre tank is way, way, way, way, way too many. Plus, now you are starting to cycle, so the ammonia levels are deadly, and the fish poop and dead bodies are further driving the ammonia.
You should take back almost all the remaining neons.

 

[achase]

I agree with Laura, that 30 Neons in roughly a 13 gallon tank is way to many. The behavior is probably a combination of stress and schooling behavior like prsturm said.

Like Laura said you should take back most of the neons and then complete your fish-in cycle. Or you could return all your fish and begin a fish-less cycle. Which you could read more about here.