My One spot foxface has been through alot, but recently he has been extremely healthy though always eating, nice and chunky, active and eating algae. Today after coming home I saw a large lump/gash on his left side near the base of his larger fin. Not sure what happened if he had a brush with a powerhead, slept wrong, or possibly got beaten up. He is the largest fish of seven in my 86 gallon tank. I have'nt added any new fish in 5+ months. Lots of photos are listed below along with videos of him eating and his behavior around the tank currently. He seems to have his slime coating partially coming off of his body and you can see the film following him as he swims. He eats frozen 1-2 times a day, nori 1-2 times a week, and TDO pellets twice daily. Random feedings are soaked in selcon and angel elixir supplements. I am not sure what this gash actually is and need help identifying it and what my next steps should be. Thank you for your help.