They get big. Some quickly, some slowly. My biggest is in my avator. He was 23" at 15 yrs old. One year in the pond he has grown over two inches. My baby ID I aqquired at one inch, he's 7 after 9 months. My Imperial ID is aprx 19". SHe grew over two inches in 6 months. You might think they are kick? fish but they are what I call lifers. They live a long time and they grow.