Angel fish are not compatible with goldfish. Goldfish are not compatible with gouramis either. 29 gals might work for angelfish depending on the height of your tank. Should have a minimum height between 14" to 16" fully grown angelfish can have a body height of around 12". I had a male that was 11" in height. Also if you do get a pair prepare yourself for an aggressive pair of fish if they decide to be mates. I've never seen such aggression before from a fish. Its incredible.