I set up a 75 gallon tank approx. 3 weeks ago. I do know about the nitrogen cycle now but didn't know then. I have a fluval 406 that is running cycled media from my LFS and I also used turbo start. My tap water test at Ammonia 1.0, Nitrite 0, Nitrate 0. My aquarium has been testing at Ammonia .5, Nitrite 0, and maybe a small trace of Nitrate. I have been using Prime every 36-48 hours to deal with the Ammonia. I have a baby Jack Dempsey, baby Oscar, and a 4 inch Severum in the tank. The Severum and the JD are doing fine, swimming around and eating. The Oscar stays in the back the tank on the bottom under the filter intake. He has done that for 2 days. A couple of days ago, I did see something white and stringy come out of him. What could be wrong with him? Should I quarantine him?