Let me start by saying this is not hole in the head. I've seen and treated first hand with other fish. Now, I went down to feed my fish in the morning to see my oscar and a noticable gash on his forehead. The only thing in his tank that could cause a straight line is the air wand in his tank. I assume when i turned on the lights in the room this morning it startled him, resulting in him smashing into the air wand. The gash is maybe 3/4" across and some scales are sort of hanging. I can see pink underneath it too. It isn't deep but was enough to scrape his scales off. Now, i'm wondering what the best treatment will be? As soon as i find my camera i'll get some pictures of it. Thanks.
Don't underestimate the wonders of clean water.