I agree, it will only work in that size tank until about half grown.You should get something else that tank is too small for an Oscar.
I you di try it, once it hits about 6" you will need to do every other day 50% water changes. As a 12" + adult, daily 80% water changes.
If you don't, it will likely come down with hole in the head disease, and be scarred up as an adult.
In that size tank, only dwarf cichlids that get no larger than 6" would be humane.