I have a 55gal tank that now houses a 2month old Jd along with a 3yr old pleco and a 2month old brown knifefish. I am looking to add some color to the tank. What would make a good mate for these guys? I have been told many things at different pet stores but they are just trying to sell product. I am thinking about Red Devil cichlid or oscar cichlid. Should i introduce 2 at a time? I need advise, and quick...thanks.