Everyone is dead except rainbow shark and goost shrimp. I unknowingly overstocked taink at one time and they all got sick and passed away a week later disspite my efforts to save them. A hard lesson learned. I have a few questions now. Do I need to treat the tank before I SLOWLY introduced new fish ? I have done many water changes and now have parameters under control and at safe levels. Shrimp appear to be fine also the shark is showing no white spots or white cotton things on it. I really feel sad about what happened and I don't want to medicate water that doesn't have any fish in it if I don't have to.