OK, here's my experience with HITH. Two of my oscars had a deep hole on the middle of their foreheads and it was obviously HITH. I tried everything: changing water often, enriched diet, removing carbon. Nothing seemed to work ... until I finally relented and dropped tablets treating Hexamita and Spironucleus in. Within a week I saw the holes slowly starting to close and now they are completely closed! This article said Hexamita is largely debunked but I beg to differ here. If your oscars have HITH I highly going to your pet shop and getting those tablets. I got the Tank Buddies Parasite Clear which states: "Parasite Clear removes external and internal parasites from tropical fish including protozoans, flukes, lice, anchor worms and flagellates such as hexamita or spironucleus which cause hole-in-the-head disease." I don't believe a lot of manufacturers' claims but I believe at least this one.
