Ours more than doubled in about 7-8 months. Look at TazD's thread around here, thats our tank (and the thread is about the recent demise of our bala
)
He was about 7" when he wedged himself inside an ornament somehow. I have a 75g tank and was concerned about just having ONE bala shark. I am a relative n00b to aquariums (only had it about a year) but the two balas we had (one died to disease and harasssment from a red tail black shark) otherwise did very well on there own (I know, not very good track record since they bellied up, but I am sure both times were our fault due to ignorance, one got stuck in an ornament, and we did alot of research and thought the red tail would leave him relatively alone if the red tail was by himself(red tail black sharks are also the one or many rule), well, it didnt work out that way. Since there were no other red tail sharks to play with, he tried to play with Mr Bala shark, and well, bala's are just to skittish and afraid to play back, he was always running from him, particularly during feeding time.)
As I said, every bala shark we've seen or owned are VERY skittish and shy and they are POWERFULL swimmers (and jumpers, so have a covered tank!) Any overly rapid movement and he would dart from one side of the tank to the other in the blink of an eye, VERY QUICK.
This becomes dangerous to them since they will literally bang them selves against stuff, even the glass and potentially even knock themselves out.
Since I dont think I, with a 75g, have enough room to let 3 or more grow, we are planning to stick to one. They SEEM happy enough, and ours always just hung out and played with the tiger barbs just fine. and because of his size, the barbs seemed to not harass the bala at all.
I love balas and think we are going to give one more try with one of them.
Hope this helps.
EDIT: Id also note to the original post, they are skittish and extremely passive in my experience. They may play a bit and school, but I have NEVER seen an ounce of aggressiveness. though we were keeping just one at a time. I dont have first hand experience of them in groups. 60g would be enough to start them in, but when they hit 7+ inches, I dont see three of them being able to dart around enough in that size of a tank (or even one!) so unless youll be able to move them or trade in to the LFS, might not be a good idea. My experience is these guys need LOTS of room to run, ie. tank LENGTH maybe more important than anything else. They are beautys though!
Again, just my experience, and hope it helps.
