I've been away for a few weeks and haven't been able to change the water in my goldfish tank.One goldfish,i've had for a long time,is lying on it's side at the bottom of the tank.The other fish look fine.I've changed the water in the tank.I took the sick fish out and put it into a small bowl with salt and a lifegaurd treatment,but i'm starting to think maybe it would be better back in it's regular tank.It won't eat and has started floating to the top of the bowl,then swinmming back to the bottom and starting over.About six months ago it had a fungus overgrowth on its mouth and I had to cut it open.It survived,so I know it's a fighter.Please help!