He has done this a few other times since I put him in my 75 gallon 2 weeks ago. He backs up, yawns, darts forward really fast and pieces of slime coat come fling off him. Not sure why I did a 20 gallon water change and used stress coat and TLC in the water. He has been really weird since I transferred him to my 75: coming out during the day, hasn't eaten in 14 days (since I put him in), and shedding slime coat. What the HECK is going on with this fish lately!?!?