You can plan on a good 1/2" per month (some months may be more, others a little less), until about 11-12", then it will probably slow down. That's about what my male did from when I got him at 5". You may have a little better growth than that, based on mine going through a time of minimal eating when he decided to breed at around 10-11", and then not knowing his growth and age when I got him. He's about 13" now, and I've probably had him a year and a half or so.