Yes, you would need a big tank. I have never kept smallies, but from what I've gathered of them, the temperament should be about right. The real problem is gonna be temp. Smallies don't do well at a higher temp for very long. You might need a chiller, depending on ambient temp of the tank. Some tank parameters would help, like size, temp, and decor. Also, the LMB get larger than the smallies do, so there might be some problems there, but if you get them small, they should do okay.