i know its not hole in the head cause i have had them for 2 months and have feed them live food twice. it seems to be like what stoopid said, the medicine i got it for rid of parasite/ich, they had some slime and also went going crazy and got cuts from rolling around on the gravel and decrocations, i took the water up to 85-86 which they seem to love and are more active, the slimes seems to be going away, one of them the hole is under his mouth and the other is close to the gills and or on the gill flap but i don't think its anything to serious cause one had it when i got him, besides how do you know if its a him or her?