Nitrite level that kills

[peppermint]

My quarantine tank is going through a mini cycle. The nitrite level was at 1 yesterday...I did a 40% water change and the nitrite is now at 0.5, ammonia 0. What level of nitrite causes fish to die from its toxicity... Should I do another pwc or wait till it turns to nitrate?

 

[BigJim]

I'd do another PWC. I'm not sure what levels of nitrite are lethal. It really depends on the hardiness of the fish. A 50% PWC would get you down to 0.25ppm.