Strange Nitrite Spike.

[Shaddex]

Recently took 20 adult corys out of my community tank and put in 10 neon tetras.
Reading 0,0 before removing corys.

Nitrite is now 2ppm after 1 day. Ammonia still 0.

4 year old mature tank, with no issues since it was cycled.

Any ideas other than I've disturbed the sand ?

 

[Shaddex]

Stupid Mobile phone Double post..    Mod's Please delete on

 

[DrRob]

Stupid Mobile phone Double post..    Mod's Please delete on

 
And done.
 
Interesting. Nitrite test kits can be a pain for misreading occasionally. How are the neons? I'd have thought that 2 ppm would have them at least gasping and probably long gone by now.
 
Other question is how much of a mess did the cories make you make while you caught 20 of them? Could be a disturbed organic layer from having to chase them around that's messed things up.

 

[Shaddex]

All fish in the tank are fine.  No Nitrite poisoning symptoms etc.
 
I took a lot of bog wood out of the tank when I was catching Corys and I suspect Ive dislodged something.
Gonna water change and see what happens over the next day or so.