If the difference between my first Oscar and my new Oscar is directly related to my care, I can understand how Oscars end up at either the common 12" size or a nice monstrous 15" or more. I "powerfed" my first Oscar and changed his water like a maniac to control the nitrates. He was 13" after only 12 months of life, but got HITH and it wouldn't go away. I had yet to learn the importance of buffering my water. My second Oscar, I did not powerfeed. Instead I struck the balance between a rounded diet and light feeding with minimal water changes for better stability. He's about 12" now at a year and a half old, but honestly looks far healthier than my first Oscar did. There are so many factors involved with growing out an Oscar!