he had hole in the head a while back and was treated and the holes are gone... but now one of his nostrils is completely red and closed up.. looks like a sore of sort.. not a hole, is that another form of hole in the head or could it be something else?.. im doing major water changes often.. he is a massive oscar and upwards of 13 years old so i dont know how much treatment i wanna make him deal with if its something major
I think you should test your water first and get your readings! When you get them try get your NH3 & NO2 to 0ppm (anything above that isnt acceptable) and your NO3 as close to 0ppm as possible (20ppm and under is usually what is recommended with Oscars!) That might involve doing large 70% water changes every day or two!! It sucks but its best for the fish!!
Id also start using a combination of both pimafix and melafix to try help with the soar on its nostril?! Try mix its diet up a little too! Poor diet and water quality issues is probably the main reason the Oscar has what it has at the moment?!
Hope this helps, great to see a 13 year old Oscar btw! Shows you have been looking after it!!!