My male personally only got to 10in before he passed away at 2 years old. I have however personally seen a red dragon FH that was 16in for sale at one of my lfs. The guys had his tank crack and just decided to to sell the FH along with 4 8-9in tinfoil barbs. Sadly the store shuved em all into a tiny lil 10g sale tank where the FH then decided that he didn't want roommates anymore and proceeded to much on their backs till the spine was showing on a couple of em.Just my $0.02 ,if you keep up with water changes a 55g(48" x 13" x 21") will be fine for a FH.The largest FH i've seen was a 12" red dragon imported from Thailand.I believe it took around 5 years to get to that size.My buddy received it at received it at 3".You've got time,when the fish starts cramped start looking for an upgrade or give it away,it's as simple as that.Fish don't feel complex human emotions.