Sorry for not giving any updates, but I've been very busy over the last few weeks. Anyway I finished the prazipro treatment, then moved the GT to a quarantine where I treated him with naladin (naladixic acid), as one of the articles suggested, and then a combo of ich-x and furan 2. The whirling still remains, but he doesn't seem to do it as often. He also still eats very well and shows no other symptoms. I moved him back into the 55g tonight. I'm guessing that it is related to some damage from when he bumped his head.