awww poor baby
my guess would be he bumped into somthing really hard
or at the very worst it could be a fungus or infection may be hole in head diesease? i certinly hope not though
"Hole in the Head - HITH, sometimes referred to as Head and Lateral Line Erosion - HLLE Small holes or indentations on the head of fish, advanced cases may show markings along the lateral line of the fish. They may stop eating. There are many theories out there, but no conclusive scientific evidence as to what exactly causes this disease. However, it may be attributed to poor water quality, lack of proper nutrition and/or the use of
activated carbon for prolonged periods. However, there have been no scientific studies about the effects of the prolonged use activate carbon causing hole in the head, it's just speculation. Be sure to give your fish the best water that you can by performing frequent water changes. Give them vitamin enriched foods and change out or stop using activated carbon."
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I don't think it's fungus. And he has as voracious an appetite as ever, water is good, I feed a variety of foods (
