I keep those two together but in a large tank (145gal, six footer). I wouldn't let them in a small tank. However I managed to raise 9 juveniles (Silver Dollars) with sub-adult Angelfish in a 30gal wide tank. It went OK for a couple of months until... the Angelfish paired-off. They turned nasty big time with the SDs. Those are the ones that now share peacefully a large enough tank to keep them happy.
Fish that I keep in tall tank with paired-off Angelfish (over a year now with no problems) are schools of Corydoras (Panda, Imitator), Kuhli Loaches and a male
betta. I kept there a school of Harlequin Rasboras but the Angelfish terrorized them so I moved them to a Community tank.
Pepetj
Santo Domingo