Sorry i have failed to mention i have had this fish for nearly 8 weeks which is long enough to see the nitrates stablise. I am new to keeping oscars but i did my reaserch. you say you had trouble to keep two oscars in a 55 gallon which i can understand. im 7.5 gallons short of 55 us gallons (if thats what your going by since your american) I scanned the internet and asked alot of people that are NOT selling me anything and found the rule says 55 min for one oscar but people do keep healthy oscars in smaller tanks. Half says you can and half say you cant. and people that say you can have. people who say you cant have most of the time never tried and are just going by t rule, which is why i asked. Im not stupid and i can figure out what seems possible or not. I have overstocked in the past not knowing any different so i know what to look out for.
You and I both know that's extremely unlikely. 