That is how our upgrade went. After I downsized a 100 gallon I picked up a 29 gallon bio cube. Great tank. My son added a RBTA. About 6 months in we found a 2nd. Few months later a third. Bought another 29 gallon bio cube. Moved one over to the new tank after a bit and while the original held steady the new cube had a another spring up. We held at 2 in each for a bit but after a couple years I consolidated the tanks into a 40 breeder. This was good for about a year until they started to split again. At one point after giving a couple away we held steady at 8 when I said enough - planned a 210 gallon.
Oddly enough once I moved them into the 210 no later than a week goes by and I ended up with 12

While the cycle was completed I'm guessing a bit of stress happened causing them to react. A few shrunk up so bad that they went from a couple inches for the new/smaller fellas to about the size of a quarter at which point when it seemed they wouldn't make it I pulled them out. Now back down to about 7 or so and holding steady.
I'm guessing at some point an upgrade will be in the works

The 40 breeder is a good choice for BTA's I found. Unless they just get split happy