I am stumped. I added more water to my 125g, I had it sitting at 80g incase I had to do water changes while it settled. After a month of no spikes and everything seeming calm I decided to add water to the tank to bring it up to 125g. I used dechlorinator and nothing else. Readings are now ammonia 0 Nitrite 1 and nitrate under 5. I dont understand where the nitrite has come from all I did was add water to the tank and I dechlorinated the water before I added it to the tank. I have been doing frantic water changes as the fish have all been at the top of the water. What did I do wrong and how can I fix it.