2 dead black neon tetras

[volantares]

Hi everyone,

I had a tank with 4 black neon tetras (i know i should have more) and 2 guppies (lets assume they arent to blame unless this is a physical cause.)

My tank is about 30 litres.

All was fine until I failed to change my water for one extra week about 5 weeks ago. 2 weeks ago I notice that one tetra has disappeared entirely which results in me doing a 50% change immediately as well as a search for the fish to no avail.

A day later I noticed my smallest tetra is deformed at the top of their mouth but I thoufht they could feed ok... although it turns out maybe not. I originally thought maybe there had been an altercation during the disappearance and the fish was injured.

I have done another water change yesterday and today i find my sick fish is deformed to the point of not having a mouth like a tetra and the eyes look larger too. I have euthanised the fish but am concerned I need to treat tank before I add new fish.

The photos arent great but hopefully it is enough to determine causation. The other 2 slightly bigger tetras are feeding normally and seem fine.

Apologies for the bad photos the fish was scooped into a wine glass.

Thanks for the help.

 

[V227]

I think that what appears to be a mouth deformity is actually the end result of a bacterial infection.

 

[King Fisher]

Looks like mouth rot likely associated to columnaris.