is it a he or a her????....my male is 8'' in nine months and my female is 6.5 to 7inches in nine months. if it is only 7'' in two years...then he's a she.
Growth rate has to do with the quality of nutrients and the mount of water changes. If you make partial water changes to the tune of 1 per month, your demp will grow slow, if you change 25% every other day, it'll grow like a weed, no matter what size tank (up to a point).
The rumor that haits grow slow has been bantered about.
In less than a year my female hait went from 2" to 9" with good quality varied diet and water changes every other day.
Generally really slow, even if they are a good eater. I haven't done the water changes every other day as suggested above so I cannot vouch for that. My JD is growing real slow though, maybe an inch every coupld months.
I agree with TrikkyMakk. My two JDs grew pretty slow, my female slower than the male. I got my male about two years ago when he was 2", and now he is about 8 or 9". The female I got about 1/2 a year ago when she was 3", and now she is about 5". So it's a pretty slow but constant growth for the most part, but I also don't do water changes every other day.