Ok very late to the party here but a few comments to add. A 6'foot tank as most 125gs are, would be a good start to begin growing out the balas but even then in my opinion would be too small once they fully mature.
They grow up to a foot long or more & are very fast swimmers who spook very easily. They have been known to shoot across a tank when startled & slam into the opposite side.This coupled with the fact that they can jump out of the water in the process makes it hard to keep in a covered tank.
I love these fish & have had them in the past in a 125g but now feel they should be kept, if at all, in something way way larger.