We rescued this unwanted Oscar today; he had been at a local pet store; in clean conditions; but whoever had him previously, who got sick of him when he got too big, didn't. Now he is going into our tank, which we keep clean (125.) He is fine w/ our oscar, White Thing; they are actually exhibiting breeding behavior and not fighting right off the bat, so I have a good feeling about it.
I researched hole-head a lot and found that monor stages like this usually will go away if husbandry is improved. We use a varied diet of live feeders, and JumboMin (by Tetra) food specially made for them. Also, occasional insects and worms.
So is anyone knowledgible about hole-in-the-head? Here are some pics.