Bonsai translates to grown in a pot. Some bonsai trees are quite large actually. I've heard of 1:1- 1:1.5 and 1:2 but numbers really do nothing for me. I've noticed Bonsai FH's have more of a proportional round small size (striving for a circle)- where short bodies tend to look like a head connected to a tail with fins somewhere in the middle. Neither are good indicators of quality but Bonsai is harder to accomplish and seen less. I always thought the short bodies were failed bonsai, but I've been told that is not the case.
