Neon Tetras bullying/dying

[bikeman]

I rather foolishly changed my filter a few days ago. I have an established tank and even soaked the new filter in the tank before replacing it. Nevertheless that old adage 'if it aint broke..' seems to apply here because all the fish afre now a bit sick. The bigger ones are darting about and teh smaller ones lie at teh bottom.

The main problem is that there is one neon tetra that is bullying the one's that are a bit sick. He has headbut and nipped tem so much their fins are all tattered. Is this normal behavours towards sick fish? Even by normally placid neons?

Any suggestions short of flushing the bugger?

 

[Irishlax627]

You could try getting one of those side attachments that hang on the tank. This way hes still their but he cant get to your fish or you can quarentine the really sick fish in anouther small tank if you have one. (I use those Betta tanks for small fish to quarentine them in before I put them in the tank or when their sick.) Try the hanging attachment because the longer he bullies them the more stressed they will get and more of a chance they could die.

 

[Miss Dib Dabs]

When replacing a filter you should leave the old one running with it for approx 3 weeks so the new one has a chance to establish the bacteria it needs. Chances are your ammonia and/or nitrItes are on the rise. Have you tested for them?
Do small daily water changes around 10% until everyone picks up again and test the water params!
Hugs,
P.