I have 6 RBP and I have them in a 75 gallon tank. They are still pretty young and small, I would say about 3-4 inches. They are growing very fast as I expected. I have a 125 gallon tank already in my possetion which is 72.5"Lx23 3/8"Hx18"W I am about to buy a 120 gallon tank that is 48"Lx24"Hx24"W. Which is the better tank for the RBs?