I haven't lost anymore fish, but they are still acting very lethargic. Come to think of it a few days prior to them acting like this I washed out the sponge filter in a bucket of tank water that has been in their for a few months. Could that have removed most of the biological and restarted the tank? My nitrates were up to 40ppm after that and now they are zero along with the ammonia, but the fish still aren't acting like they used to? Any advice?