Hi all I got 2 oscars in a 90 gallon tanks I do weekly water change they both got tiny holes in their head and from time to time thses holes turn white inside then it goes away what causes it and how can I get heal them
You are under filtered, and you are not changing enough water. Oscars are big waste producers and it looks like you have a pleco in there as well. Also a big waste producer. HITH is caused from dirty water. I would get some metro, and do some research on HITH, http://www.oscarfishlover.com/hole-in-the-head-disease
I would also get more filtration, change 50% to 75% of the water twice a week, and seriously consider re-homing one of the oscars, and the pleco.