When you say you cleaned the filter and changed the media - did you actually clean the filter and replace media? If so, you likely lost most of the bb that made the tank an established one.It was an established tank that was a mess,Cleaned up the filter, changed the media ect.. I changed the water almost completly 2 times by vacumming the gravel so much. Added prime as bottle says. I've checked my ammonia = 0, nitrites = 0, nitrates =.5