Can a bala shark be kept as a solitary specimen, and if so, what the minimum size tank for one fish? I'm most likely not going to do this, but I've been curious for days and this kept me up all night.
single specimin is a bad idea as they become even more skittish. My experience is that you need a shoal of 5 or 6 at least to get the best out of them.
I would say any tank needs 6 feet in length and 18" front to back as a minimum, but I would not want to put mine in anything less than a 6x2x2.
No the larger the group the better. The problem with this is that most people simply don't have large enough tanks to have a decent sized shoal of bala sharks, i agree with andy that a 6x2x2 ft tank is a good minimum size tank for bala sharks, these are big shoaling fish which can easily grow to a 1ft long each.