Quarantining new fish for a while in a separate tank is useful if you have valuable stock in the main tank that you don't want to jeopardize. With only two fish left in the main tank, I am left to wonder how much sense it makes to keep the new fish separate. Especially if you move the H. elongatus pair right away to the 40G and the rest to the 135G, you are left with only one old fish in each tank.