I should have placed him in the 10 gallon to grow, he died today. I came home from work, he was sitting on the bottom alive but kinda sitting at an angle. I thought it was the current so I shutdown the pump, he just stayed there. His breathing was a little strange but nothing to be alarmed about. I watched him while I feed and he never tried to move or eat. Then I saw him move a little, and then I saw him swim for a minute. I thought maybe I was over reacting and he was okay.
I did my normal water change, and when I finished he was dead. The tank drop 2 degrees during the water change.
edit: while he was just sitting there I had my face close to the tank to inspect him, My O and Tex came up to me multiple times and never once bothered him. I never saw any of the other fish mess with him, not even my bully rainbow shark. He was in my tank for 2 weeks. Dang I just realized I could have returned him, but I flushed him, oh well live and learn.