George and Mildred the two I had in the 80's lived in a 6ft x2x1.5 ft tank they went 15 and 13 inches a piece, I used to tap the top of the tank water and they would come to the surface to be lifted out for cleaning, the reason that they were called G & M was that they used to mouth lock and break anything fragile in the tank like a waring couple. They used to sit and watch me when ever I was in thr room and always seemed to know when I had some river shrimp for them. They did have a Clarius as a tank mate that was at 18 inches to big for them to beat up. Incidently my cat at the time got a shock not from the Oscars but the Clarius which knocked the lid of the tank so hard that the cat was launched off the top of the tank.