With the room they have, good nutrition and great water, they'll be 10 inches in about 3-4 months.
I have personally seen 2'' of growth in 1 months time...
Between 6-12" they look like they grow bigger overnight....
And then you get the "terrible 12's"...if you think you have an aggressor now, just wait till they hit that 12" mark. they really get an attitude...