MY PUFFER HAS A LARGE BLACK SPOT ON HIS FACE

[srmembership]

So our puffer fish at our gym has in the last couple of days developed a black spot on his face. I attached a picture where you can see his face used to be clear of this abnormal spot. AGAIN, THIS PICTURE IS NOT SHOWING THE SPOT OUR PUFFER HAS DEVELOPED!! I am going to try and take a picture of him when I can to display what he has developed. He is not eating like he used to, he keeps his body in a u-shaped form, he'll sit on the bottom of the tank and appear as though he's moving his fins to swim and seems to rub his face up and down on the glass. We have a "fish-guy" that supposedly monitors our fish and takes care of the tank but I don't know how knowledgeable he actually is. We feed him thawed-out silversides and crill. Can anybody tell me what might be wrong with him or if maybe it's the food we're giving him? I did some research and saw some of the typical types of food being fed to puffers but ours doesn't seem to have developed teeth yet, he is still fairly young i believe. appreciate all the help we can get. i think we're going to eventually assume the position of "fish-guy" and take care of our buddy ourselves. There are also some other fish in the tank and maybe they bit him overnight? There are a couple lion-fish, clown fish, and i don't know the names of these three silver fish that always stick together but their bodies are silver and their fins and tail are yellow - they're trouble. thanks again, look forward to curing our puffer!

[LilGreenPuffer]

Please don't double-post.