Can I put my 4" silver aro (currently in a 55 g himself) in a 120 gallon tank with 2 6" oscar + 1 4" red terror + 1 3" midas? I also have 2 green terrors and 1 firemouth and a pleco in there. I will get rid of the these 3 if too crowded. I want to use the 55 g for my 4 dollar size pirahas.