so I've got a 10 gallon tank that housed a small peacock bass for a couple weeks. I kept it running after I took the fish out and a week or so later put a couple sick fish in the tank to treat them. Within a couple hours they were both dead. I also added a large sponge filter that had been running in my 180 for a couple months to help with the waste in the tank. We check the levels and all was good except nitrites were off the chart. I did a 70% water change and took the dead fish out last Wednesday. I left the sponge filter running and now almost a week later the nitrites are still way up. How long should this last? I want to throw some guppies or something in to keep the cycle going but at the current levels they will die. Any thoughts?
