Why does my aquarium fish have a hole in his head

1) removing a few fish from the tank (I had extras in that tank because my 55 gal sprang a leak so I spread the fish from the 55 into each of my other tanks till it cured and was safe to put the fish back in),

2) frequent water changes with good quality water that I purchased from an aquatic pet store (Reverse Osmosis water with essential minerals put back in),

3) adding vitamin and mineral block that releases into the water slowly like a vacation feeder (I will have to find out who makes it. I think it is by Aquarium Pharmaceuticals Inc.

4) time and patience.. bring the water quality up to where it should be and slowly things will get better. Everyone I talked to told me that I should just put my fish out of her misery. I couldn't bring myself to do it, and now I am glad I didn't. My angelfish have gone on to spawn again, so I have a bunch of new baby angelfish!!

Good luck